the XTE has a lower KV motor because it is heavier. top speed is really only 5-7mph less I believe. I think the 8e does more like 45mph. Maybe it can hit 50mph with a good set of 2s lipo packs, but I seriously doubt it will do that on the stock 20c 3200mah packs. I know the earthquake (slightly heavier, huge tires) hits 40mph.
As foxy mentions, the 8e's are known for diff issues. These do apply mostly to the earthquake, as the huge tires put A LOT of stress on the diffs. The buggies smaller tires will ease the stress. But if you haven't looked up "redcat diff shimming" on google or youtube then please do so. Some of the 8e's ship with diffs that have play in them. If you don't shim them with a XTR washer/shim kit then they wont last more than 5-8 packs (depending on how you drive)
It also helps a lot to buy the hobbywing program card. This will let you adjust the punch control and braking force on the ESC. The stock settings are too high IMO. Raising the punch control will soften how motor applies power when you hit the throttle. And the stock brake setting is so strong that hitting the brakes in the air locks up the tires and makes the buggy nose dive hard.
So, look up diff shimming, and buy the program card. While the XTE is the better buggy, the backdraft with a little work can run well. Another RCU member (in Canada I think) raced his and did well.