Unfortunately, if you ask 20 guys this question....you're likely to get 20 different answers. There is no "best buggy" out there....it's a myth ;-) They all drive differently, they all suit one driver better than another driver. No matter how durable someone claims it to be....if you drive it into a wall or can't stay on the track with it....you will break it.
I have had my Hot Bodies D8 Hara for 16+ months now....racing it at least 1-2 times a month...sometimes 3-5 day events...sometimes just 1 day events. I still have the original suspension arms on it....and have barely replaced any parts. I recommended the buggy to a friend...who promptly broke both front arms, a shock, and a diff case in the first 15 minutes he had it on the track.
Best advice I can give you here is to get a brand that either you can get parts for locally....or have a good online source for parts and don't mind waiting while they get shipped.
Here are MY opinions of some of the more known Buggies out there:
Losi 8ight 2.0 - Awesome handling buggy if you know how to drive (read agressive). Very durable, even if you like off track excursions. Parts get very sloppy...very quickly....and unfortunately that slop is what makes it handle so well. So if you like a tight car....bypass the Losi. It will never be tight.
Mugen MBX6 - Great buggy for just about everyone. It's good with aggressive drivers and tame drivers. One of the most durable buggies I have seen, and a proven design backing it.
Hot Bodies D8 - Great budget minded buggy that is no slouch on the track. It's not the fastest, or the lightest, but it's a great buggy that can be driven with the best of them if you have some skill. Cheap parts make it very attractive, and it's been extremely durable for me in the 16 months I have owned mine. Only durability issues it has are crappy stock CVDs. Buy the Tekno axle stubs and be done with it.
XRay XB9 - It's an XRay. What else is there to say? Top quality parts and workmanship. Excellent handling buggy, but not for everyone's style. One of the most durable buggies on the market and the fit and finish of their parts are second to none. Only downside is the parts are very pricey and almost no one stocks them locally that I have ever seen.
Kyosho MP9 - Great buggy, but way overpriced. Never driven one, but lots of locals have them and do very very well with them. Hardly ever see them break either.
Those are probably the "Top 5" in my opinion. Agama, JQ, S-Works and fill in your next favorite here are all good and competent racers. Just need to find the buggy that fits YOUR driving style. Go to the track and beg and plead to drive a few different brands.