RE: Help with beginner (somewhat)
I run all 1/10 scale, but I admit it is due to cost.
1/8 scale can handle taller grass and rougher off road better, but costs easily twice as much. Still, $700 is a good budget, and you could get into 1/8 scale for that.
In my opinion, electric is better than nitro for every reason. Speed, reliability, lack of noise, lack of pollution, no need to buy fuel @ $30 a gallon, no tuning needed. But I drove electric all my life, and I'm an electrical engineer.
Your best bets in my opinion are the HPI Savage Flux or Traxxas E-Revo brushless. They're both 1/8 scale monster/racing trucks, and are both capable of 60+ mph with 3S Lithium Polymer battery packs.
One thing I'd like to mention is that these high speeds seem really great to start with. But 60 mph is REALLY fast. At this speed, it is not fun for long. You're going so fast, all you can do is run up the street, slow down, turn around and run down the street. In other words, you'd only do speed runs. It gets old fast, and crashes are catastrophic. Plan on major damage to your vehicle, and maybe major damage to the vehicle you ram into. (e.g. parked cars)
If you really want to do this, you're probably better off with a brushless touring car. Something with a really low center of gravity and precise steering.
What turns out being a lot more fun is bash-racing at 30 mph max. Set up an offroad course somewhere and either compete with buddies or try to get the best time and best control over it. Put in a couple jumps to keep it challenging.
The beauty of the Savage Flux and Brushless E-Revo is that you don't HAVE to go 60 mph. You can gear it down a bit and use 2S LiPo packs for a top speed of maybe 40-45, but with a lot of torque and a lot of control. You can go on road or off. Grass doesn't slow them down much at all, as they have big wheels and great ground clearance.
The Savage Flux is a better value, but the lay-down shock design of the E-Revo is a little better.
In 1/10 scale, you get a lot more for your money, at the cost of a bit of offroad prowess on rough terrain. I went with the HPI E-Savage on sale for $210. Spend $200-300 more, and you could have a great charger and several sets of LiPo batteries for lots of run time. Plus some money left over for repairs, RPM bumpers, etc. Still very good offroad, as it is pretty big and 4WD. I was blasting around my mom's yard and street in the snow today, and literally stopping traffic. Everyone just had to see what it was, and it is just sporting the stock cheap brushed motors and cheap 6 cell NiMH battery packs.
Spending $680 in the 1/8 scale brushless E-Revo leaves you with no budget left over for extra sets of battery packs or spare parts.