I don't agree with the Ofna having a better engine. If you break in the VTX engine properly, it's a beast! It does take a little gentler break in than the average engine, but when done well, it will run really strong and will last. I do have to admit that the carb on the VTX engine ain't the greatest.
crazy4wdracer does pose a good question: are you planning on racing or on bashing? If you are planning on racing, I would personally recommend the VTX. The Hyper 7 is an older design buggy that will not handle as nicely and smoothly as the design of the VTX. If I compare my VTX with the Ofna from my buddy, the Ofna is more of a tank. Both buggies do hold up well for bashing. VTX is coming out with a race roller (VTX-B1X) soon, which would be an excellent choice if you plan on racing. It will have newly designed plastic, diffs and chassis pan. It will be cheaper than the RTR, but you will still have to buy the electronics and engine, which is something you will end up replacing on both the Ofna and the VTX if you really get into racing....