If you "serious" about modelling rubber, MARC and ABAQUS and you only real choices. Both packages allow you to do pretty much anything you want, however each has its own unique set of strengths and weaknesses.
If your unfortunate you may find your decision restricted by financial considerations. HKS "prefer" licenses to be leased while MSC prefer their licenses to be bought. So it all depends on how long you intend to keep the software and how many licenses you are after. Either way it's extremely expensive if you get it wrong.
ZattleBone