I've read a few PM's and forum posts recently where our members claim that a longer-ester variant of the same compound are more effective than the shorter variant (i.e. using testosterone enanthate and testosterone propionate).
This simply isn't true - therefore i have outlined a few points below to help illustrate this.

Here's my roster:

1) Introduction
2) What is an ester?
3) What is the purpose of an ester?
4) Number of atoms per ester
5) Ester half-life
6) Why stick with long esters?
7) Why use short esters in pre-contest prep
8) Prop-potency
9) VALUE FOR MONEY (VFM)
10) Sustanon, is this better?
11) What's wrong with Sustanon?
12) Conclusion

Choosing an ester for your next AAS cycle is an important factor to consider. Ester lengths have the ability to define/redefine our muscular appearance, while also providing either a slow release of the main compound to which the ester is attached to or releasing the compound instantaneously. The general rule is, the longer the ester, the longer/slower the release of the main compound - products such as TNE ( Testosterone No-Ester) and Testosterone Suspension have no ester attached to them, and therefore will be transported around your body instantly.

An ester is simply a chain of atoms made up from both carbon and hydrogen - the ester is then attached to the main compound (in this case using AAS steroids - whether it be testosterone or trenbolone for example) at the 17-carbon position. Longer esters have more atoms in its chain at the 17-carbon position, thus increasing the time for the human body to break down that particular molecular chain before it breaks down the main compound.

I hear you ask, what is the purpose of an ester? - Well, esters increase the half-life of the compound it is attached to, and by doing so, one can pin (inject) less often, while crucially maintaining stable blood levels. Products like testosterone propionate require more frequent injections (preferably ED/EOD) in comparison to Testosterone Enanthate (E3D/E4D).

In order to illustrate my aforementioned point, i have presented below a list of the number of carbon atoms situated in each ester:

Formate: 1
Acetate: 2
Propionate: 3
Butyrate: 4
Valerate: 5
Hexanoate: 6
Heptanoate: 7
Enanthate: 7
Octanoate: 8
Cypionate: 8
Nonanoate: 9
Decanoate: 11

Additionally, the data below represents the ester half-life. (The pattern to notice is the more carbon atoms there are, the lengthier the half-life)

Formate: 1.5 days
Acetate: 2 days
Propionate: 3 days
Phenylpropionate: 4.5 days
Butyrate: 6 days
Valerate: 7.5 days
Hexanoate: 9 days
Caproate: 9 days
Isocaproate: 9 days
Heptanoate: 10.5 days
Enanthate: 10.5 days
Octanoate: 12 days
Cypionate: 12 days
Nonanoate: 13.5 days
Decanoate: 15 days
Undecanoate: 16.5 days

At this point in time, you may have came to the conclusion that there is no need for short-esters, since there simply is no need to be pinning unnecessarily. However, there are many more factors to consider before you begin purchasing your long-estered variants, such as the rate of aromatisation/estrogen conversion and blood level volatility for example.

The evidence for this argument results from understanding what esters are - the main variable in comparing esters is their affinity towards water retention, and at what rates the sub-cutaneous water retention is experienced. Experienced AAS users will strongly agree that the water retention experienced through running a long-estered variant such as testosterone enanthate in comparison to testosterone propionate (whereby the main compound in each product is testosterone) is significantly higher. Therefore, these experienced AAS users will tend to use the longer estered variants in their off-season and the short ester variants towards pre-contest preparations. Additionally, these sides such as increased water retention from long-estered testosterone help increase the chances of obtaining other sides such as gyno.

Another point to consider, which i have read more frequently recently is that some of our members claim that shorter estered variants are more potent than their longer estered counterparts. Well, not necessarily since they have the same compound to which the ester is attached to - however, the main difference is that in a 10ml vial of testosterone propionate, there will be a higher percentage of testosterone in the vial, in comparison to testosterone enanthate whereby there is an increased amount of ester weight.

When an ester is attached to a compound the ester makes up a percentage of the total weight of the compound - for example, testosterone cypionate contains 69.9% testosterone per mg, whereas the cypionate ester makes up 30.1% of the total weight. However, testosterone propionate contains 83.7 mg of testosterone, per mg and its ester weight is 16.3% of the compound. Additionally, since shorter esters release the parent compound into the human bloodstream at a faster rate, gains are recognised at an increased speed.

Milligrams below are the estimated amount of active hormone per 100mg of hormone and ester.

Testosterone Base: 100mg
Testosterone Acetate: 83mg
Testosterone Propionate : 80mg
Testosterone Isocaproate: 72mg
Testosterone Enanthate : 70mg
Testosterone Cypionate : 69mg
Testosterone Phenylpropionate: 66mg
Testosterone Decanoate: 62mg
Testosterone Undecanoate: 61mg

Below is a list of the more commonly used esters, which have been grouped together according to the percentage of testosterone they contain per mg - additionally, i have added breakdown of how much money is spent on the product and how much is spent on the ester (based up on RRP in USD ($) of a 10ml vial using common dosages - Rested Retail Price (term used loosely LMAO).

Percentage of Testosterone per mg - RRP ($) - Value of test - Value of ester

No Ester: 100mg---------------------$45--------$45-------------$0
Propionate: 83.72mg-----------------$35--------$29.3-----------$5.7
Phenylpropionate 66mg--------------$45---------$29.7---------$10.3
Enanthate: 71.99mg------------------$45--------$25.2-----------$19.8
Cypionate: 69.90mg------------------$45--------$24.47----------$20.53

Now, you may say, that maybe i should use a blend which encompasses multiple ester lengths such as Sustanon. Sustanon is great for pinning E3.5D/twice a week, but there are three faults;

1) Since it is a blend, the measurements of each compound are much weaker, thus producing results in inefficient amounts when compared to a single estered compound.

2) Pinning twice a week will make you're blood levels volatile, since sus contains prop, and I don't believe pinning ED or EOD is an option either, since there will be a build-up of longer-estered compounds in your system producing variable, un-tame results.

3) Ester length effects more factors than simply injection frequency and release rates - it also effects water retention, net protein synthesis, gyno risk, influence on estrogen conversion.

Finally, I believe that sus is not cost effective. I say this because the longer-esters take up 'more room' so to speak than shorter esteres. So, imo, if you were dead set on taking sus, then I would buy a vial of prop, a vial of phenyl prop, a vial of iso and a vial of deca and mix accordingly. This is for two reasons, to ensure that the sus is not under-weighted (like many products on offer), and to maximise cost efficiency.

Hope this helps,
P

References:
http://www.eroids.com/forum/general/supplier-introduction/BodySynthetics...
http://www.bodybuildingforums.com.au/anabolic-steroids/2993-esters-in-aa...
http://www.eroids.com/forum/steroids-qa/anabolic-steroids/why-does-every...