It is conducive to learning how to function in residency. That doesn't necessarily correlate to good doctoring, because most physicians don't practice in such settings, but it does help come audition and residency time. There also tends to be more structured learning in wards based rotations.
None of this inherently means that preceptor rotations are bad or poorly planned. The thing is, you could certainly have a really bad preceptor that basically only let's you shadow or where there's very little you can do except watch the doc (possibly a very good one) write notes because he has to hurry and finish before the next patient. Are they all like that, no, and I'm sure it also depends strongly on the field. With wards based, you could have a bad attending, or a bad resident, or a bad intern, but the chances they'd be all bad is not particularly high.
The other thing is structured education. A residency program has a teaching structure embedded in it (because they have to have one), a preceptor may or may not have one. It could work to your advantage in that depending on the preceptor, you might get to do amazing stuff that residents dream of doing. It also could mean that you have a lot of down time where you're just told "read in this room while I do X, Y, Z" or "practice writing notes that I'll never look at". It all depends on how organized the rotation is and the preceptor.
I'd also like to say that med students complain a lot. Go in expecting a great experience, and decide for yourself whether it was bad or not. The thing is, when you start hearing complaints about a specific location/doc where the complaints are all pointing out the same problems and coming from different people, that might actually mean something.