I've ran both drive lines. Personally I prefer the 2wd trx vehicles.
The 4wd trucks have much more potential for crazy power handling and race tuning. But if you want that crazy power, it's gonna cost you a pretty penny hopping it up to handle it. The 4wd is EASIER to work on as its maintenance ease was built into its design. There are however many more things to maintain and it takes a ton of cleaning because of the front tires whipping(sandblasting)tiny rocks and debris all over anything behind them. I had a bunch of fun with my Mt and sct slash platinums.
Somehow the challenge of driving a strong (2s vxl or cc power, not crazy power haha) bl 2wd truck and keeping up with the overpowered 4wds is very fun for me. Driving a 2wd is kinda like falling down the steps and landing on your feet... over and over and over 8) especially with the pede.
It has a solid drive line. With proper clutch settings the axles last a long time with 2s brushless. Yes you MUST address the floppy stock c blocks, but that and shock caps are the only glaring weak points. It's pretty easy to work on, because of its simple design. It's got a million years of aftermarket support behind it too. A big bonus is sharing parts with the kids truck if you go with the 2wd. Your the hero when his camber link bends, and you swap in yours to keep him bashing.
2wd slash chassis w 2.8 mashers or badlands and a cool emaxx body is my pick for funnest 1/10 basher in the fleet. I can't get enough...
These are my personal views. Yours will be different. Ask yourself exactly what you want out of it, and how much time and money your willing to spend on maintenance and hop ups and power systems etc. Either platform can be made pretty bulletproof with vxl power for low costs.
Check out ebay. Look for auctions, and try to only bid once at the end. No reason to fight with another bidder for 6 days driving the price up. You can get nicely hopped up trucks for less than rtr.
Another path is to buy the chassis, then build it how you want it from the start. Seems like it's expensive to buy it piece by piece, but you may wind up buying most of these parts in the future anyway. You don't need many expensive parts to build a great truck.
I know this prob won't make your choice any easier 8 (
HERE WE GO STEELERS !!!!!