For running on the street, pebbles *may* be an issue. But, running on a prepped track pebbles should be VERY few and far between and belt drive should be fine. I've run my Sprint 2 on the street and never had an issue. Maybe you'll damage/break a belt or bend a pulley but it's never happened to me. Belt drive is pretty much the standard now, there are only a few shaft drive cars left on the market.
I'd still go to the track. I bet a lot of the guys that run indoors also run outdoors and can still give you better advice with the local experience than we can give you over the internet.
You can buy whatever you want and if you only ever run it on the street by yourself it really doesn't matter. But, if you think you'll ever want to race, talk to the people you'll be racing with first.