I owned the original JBL-308s but I was able to compare them with similar monitors in the Sweetwater Music's Monitor Room.

Their new JBL Wave Guide creates a spatial sound field that none of the others could touch including the HS-8s, KRK Rokits, HS-7s (that I once owned and they drove me crazy) the PreSonuses and others.

I do agree with comment above about the Focal Alpha 65s and 80s.
I actually had the Alpha 65s then traded up for the Alpha 80s.

The Focal Alphas cost a bit more but the sound quality is amazing and WELL above the 308s, HS-8s etc.

If you have a smaller room, the Alpha 65s are really really worth a listen to.

+1

I'm very happy with mine. No plans to replace them.

I have the 308P, but unfortunately I have nothing else here to compare. They sound a bit bright out of the box to my taste, so I use them with the -2 HF rolloff. Very detailed though and with great bass extension, mine are pretty flat down to 40ish Hz. They have some uneveness near the crossover point, a slight bump I believe, which to me makes snares sound kinda stiff (opposite problem of the 306P it seems, and a bit less pronounced I guess?)

I previously owned KRK VXT6's (which I absolutely loved). I sold them some time ago because I needed the money, wouldn't do it otherwise.

I'd say mids are better on the VXT6, bass and imaging is better on the 308P.

I didn't A/B them though.

All 3 of these monitors are standard models usually displayed at Guitar Centers etc.
I suggest taking some recorded material you are familiar with and visiting one to hear them for yourself.

Do not buy low end monitors from european or american companies. They will give you small woofer or clamp bad components for the high price. Treat yourself with Sonodyne instead, one of the best all around, high end monitors. Just read few reviews that are on internet. They are not joke like thousands of Jbls fake reviews.