Depends how much cash you have.
haltech have a good reputation and reasonable price.
Motec is one of the best but not many people want to spend that much.
I have a motec m84 running mine. Previously i had a microtech, which is probably the cheapest out there and for a reason too.
Go find an engine tuner and go off their recommendation, ultimatly they have to get the most out of it for you.
They are all pretty good until something goes wrong and that is wheret the good ones shine, ie how you diagnose the issue and aftersales support.