electric or nitro rc cars?

Electric are much easier to modify and tinker with.
Nitro are more expensive, and in my opinion, electric ones last longer if they have rechargeable batteries. I've seen electric cars go faster than nitro cars all the time.
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That depends on where you'd be planning on using them. If you want to use it in the local park or playing fields, you'd want a buggy or truck.
If you'd only be using it out in the street or in a carpark, you'd be better with a touring car style rc car.

The main difference between nitro and electric is how involved you want to get. Nitro does require a bit more maintenance with adjusting the mixture screws on the carb and using after run and air filter oil and making sure all screws are tight because of the vibrations from the engine…where electric are just plug in the battery and off you go. But straight out of the box, nitro are better. Electric in my opinion end up costing you more with having to buy better battery packs, chargers etc.
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Its personal preference. I have played with both, and raced electrics for several years. The benefit of Nitro is you get realistic sound, longer run times, and speed. But, they have to be constantly adjusted to compensate for outside temperature, Driving conditions, etc…. Electrics are fun too, sure, you dont get the realistic sound, but its fun trying to see how fast you can get it going with all the modifacations, and customizations available, such as Motors, gearing, battery style/types, tires etc…. And now that there are brushless motor systems available, you can get them to go very fast, and with proper gearing, outrun nitro. Either way, you could invest several thousand dollars with either choice. And yes, I said invest, because with all the cash I spent on the hobby, I could have bought a small house or very nice real car.
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self expeirience