2nd most of what’s been said, especially getting something your local shop or good website carries lots of spares or hop-ups for so you can easily fix and upgrade it.
Electric is easier to get to grips with but your fun is limited by the number of batteries you have charged up. Nitro is smelly, lairy and loads of fun and you can drive as long as you have fuel. Positives and negatives to both.
I’ve had both and nitro was more exciting but more frustrating unless you are good at tuning engines. Also a big anti social and the 1/8th scale need lots of space – think football field, BMX track or supermarket car park.
My 1/8th scale nitro buggy with a .21″ engine would easily launch the biggest jumps at the BMX track!
Buggies are excellent for go almost anywhere speed, truggies if you want something capable of bigger stuff.
1/18th is a good scale for the garden, street or just about useable with control in a big living room.
If you are interested in 2nd hand, I’m about to sell an 1/18th scale electric RC18T with brushless conversion and loads of spares.
Associated RC18T
http://web.re-create-it.co.uk/stuff/forsale/rc18t/