Call me biased but I think your a fool if you dont go for the most expensive biggest name brand ecu you can get. Just think, once you have your fuel and ignition maps set up for good load, idle, rpm and temp reference points, you can use the extra auxilary inputs and outputs for doing mad things like making your wipers go on at 5000rpm or have your windows go up and down when you are running over 8 psi boost. You could even use your brake pedal switch as an input to tell the ecu to send a pulse to your interior lights so they flash on and off so you think your at a disco all while just waiting at an intersection. Is that madness or what?
With all seriousness, unless you have a need for the extras that the expensive top line computers offer, you are wasteing your money. Having said that, nowdays even the top line big name ECUs are very competetively priced to be within the same price range of the not so big name brands. And like I have said before, most ECU manufacturers can supply you with a computer that meets all your engine fuel, ignition and auxilary needs, you just have to request it. Then again some people like to spend the extra money for extras they dont have any use for, plus you get mad stickers for your car.

As for tuners. Unless you have a 10 year old computer that has limited ref points, your car can be tuned to run like original if not better. All computers are programmed differently but if your tuner doesnt know how to read or set up an XXmap, his dyno and gas analysier wont be of much use ( with this making the tuner the same)
You will also find that most people who say xx brand ecu are bad because of such and such, have never had them tuned properly. They are either tuned buy mates who say they know what to do, or they arent tuned at all and rely on the ECUs base map to operate.

Cheers Steve