Also take into consideration what you want to spend.
Electric is generally cheaper than nitro in the long run because you don't constantly have to buy gas, and batteries last a pretty long time. Nitro requires a lot more care with tuning and maintnance.
Onroad cars usually stay cleaner and depending on the course, flip less, however when they flip a lot can break. Off road are built more for jumping and flipping, so they are more durable when it does happen, however due to mainly being ran on dirt, they get dirt and debris in about every crevice.
If you have the budget for it, I would reccomend an electric on road/ carpet racer and a nitro off road truck. This way you can run the electric at the track and have something fun and loud to bash around with when you're not at the track.
If you have a local track, go on a raceday and talk to people, if you run into the right person, they might have an old racer they don't use anymore for sale at a fair price.
HPI RS4 RTR3/ HPI RS4 MT2/ HPI Savage 21