Haven't tried either, but my understanding is that the difference is like night & day. They're similar in that they're both pretty terrible. Better legal stuff out there definitely...
Couldn't be more different. MDAI is apparently quite pleasant in a mellow kinda way but not tried it myself. Naphyrone is shit - like MDPV only either much weaker, no euphoria and shorter-lived or a fair bit stronger and much longer-lived depending on where you get it from. I had naphyrone (NRG-1) and it's the "weak" version - felt like I'd taken Prozac but that was about it. "Energy-1" appears to be a different chemical and is generally the stronger one. Virtually nobody has a good word to say about either. MDAI is probably a much better bet but don't be expecting anything like MDMA or meph despite what the vendors claim. It's very mellow stuff by all accounts - good for a night in.