Colin, the 10.5's are much the same, go with whichever takes yout fancy, I have the Orion Vortex and it's as good as any other.

Might be an idea to "match" the ESC and motor if you are buying both as there are loads of combination deals which work out cheaper.

As for gearing, you should be looling at around 60 - 65 mmpr for an average size outdoor track. No idea on tyres as we run indoor (at around 55 - 60 mmpr)