In my opinion hgh, there has been no definitive proof the igf out there is legitimate and real, if it were superior to hgh wouldn't it be more expensive?.. I'd much rather have a floating hgh serum along with raised igf. Personally in off season / trt I run 250mg test enan weekly and 5iu angtropin daily. I get my bloods checked routinely from my endo. Hope this helps!

If need to choose one I would go with IGF1 as it's more affordable and shows unique and distinct anti-catabolic effects (refer to the articles below)

Of course the combination of GH and IGF1 is THE most effective ever combo off cycle (and on cycle), and I've seen pros who keeps 100% of the muscle mess and get denser tighter more vascular look using GH and Somedin while bridging !

(In the medical literature below you may see the unique suppressive effect of IGF on cortosol/corticosterone which the major catabolic hormone in the body)

http://www.ncbi.nlm.nih.gov/pubmed/9129466
------------conclusions -
GH and IGF-I combined further enhanced fat oxidation while reducing protein catabolism. Serum insulin concentrations were significantly increased by GH but decreased by IGF-I. GH significantly decreased serum total triiodothyronine concentrations and IGF-I significantly decreased serum corticosterone concentrations.

http://www.ncbi.nlm.nih.gov/pubmed/10571453
-----------results and conclusions
RESULTS:
Administration of IGF-I, but not GH, attenuates dexamethasone-induced protein catabolism and increases insulin sensitivity. Simultaneous treatment with GH and IGF-I additively increases the serum concentration of IGF-I, whole-body anabolism, and lipid oxidation. GH or IGF-I when given alone produces similar increases in the serum concentration of IGF-I. However, GH selectively increases skeletal muscle mass whereas IGF-I selectively attenuates the intestinal atrophy and abnormal intestinal ion transport induced by TPN. These tissue-selective anabolic effects of GH and IGF-I are associated with differential increases in protein synthesis in skeletal muscle and jejunum, respectively.
CONCLUSIONS:
Simultaneous treatment with GH and IGF-I may offer the greatest clinical efficacy because of improved nitrogen retention in association with enhanced lipid oxidation and stimulation of protein synthesis in multiple tissue types.

Without a doubt I would say both if you can afford it.

I wouldn't pick one or the other but run them both. Cycle the igf while on the GH. There is a synergy running them both.