At the risk of seeming biased....
Theres some facts you should consider:
TP/SM doesnt accept paypal
Thier resellers do but SM really doesnt make being a reseller for them an attractive prospect.
Gnax has excellent support. The DC techs are the best I've ever dealt with and they respond within 10 minutes 24 hours a day and I mean 24 hours a day.
With SM you beter hope you don't need support, because you will not get any without a lot of work on your end. Search the forum for SM service complaints.
Only plus I can give SM is thier network is probably one of the fastest available for pure speed. Gnax is very close but for me, service and personalized dealings with a smaller company who can match the level of "physical" attributes tipped us towards Gnax.