For me, electric is the clear winner. I just raced at a nitro club last weekend, and couldn't believe the noise - like hoards of large, angry bees. The mechanics were also constantly checking their cars too, so the noise continued between races too. There were electric 1/8ths running with the nitros, and they were acknowledged to be a lot faster, though with shorter runtimes.
That being said, powering anything over 1/10th scale quickly gets expensive with electric, whereas powering anything under 1/8th scale is plain difficult with nitro. What you plump for depends on the surface that you have available - get something of a scale large enough to cope with the terrain, but not so large it goes over your budget for running costs.
With bashing, runtime becomes more important - the major costs with electric are right at the start, with the layout on lipos and charger, and to get, say 30-45mins runtime, you'd need 2-3 lipos (and keep one on the charge). My preference would be for the hardcased ones, as that eliminates much chance of disaster from a punctured pack. All that will cost