WE use Penthouse Golden Nugget. We have had it for several years. My wife inserts it in her pussy and then I put my dick in and we fuck with it vibrating inside. Great fuck with the vibrations. PM me for more details of our fucking.
I really haven't had an issue with any of them. Bullet vibrators are powerful enough that they even work well on me. Of course, they don't last a particularly long time because they tend to get used a ton.
Most of the time, you get what you pay for. Cheap doesn't always mean crap, but don't expect a lot out of a vibe you got for 6 bucks when you could have gotten one for 15.
The more batteries it uses, generally, the more powerful the vibes will be. Powerful doesn't always mean good. Practice and patience is key.
Vibes with a speed-control dial are great. Vibes with two speeds (on/off) are not.
Well, I do have one vibrator that's just on/off and is pretty good. That's the little 5 inch white vibrator you're supposed to put in Clone a Willy replicas. That thing can really vibrate. Other than that, though, I agree.