There may be an association between GH antibodies (i.e., antigenicity) with mammalian cell-derived rhGH versus E. coli (e.g., Iranian Norditropin saw 8.5% antigenicity versus 1.2-2.8% for E. coli-produced Somatropin). Yet, there was no clinical relevance (no decrement in GH response [IGF-I increase] nor height velocity).
There may be some minor influence of excipients used (e.g., some rhGH formulations may use mannitol which is a diuretic) on body composition. Genotropin uses meta cresol primarily. Serono Serostim sucrose & phosphoric acid.
Anyway, with all rhGH formulations there is a "stalling" after some time (due to diminished GH response, likely due predominantly to GHBP/IGFBP dynamics, diminished phosphorylation of downstream elements to the GHR, etc.)
I think the perceived differences by formulation are largely modulated by time * dose and by nutritional and training influences, other drugs.