In their active time, the 6630M-equipped minis had an ambivalent reputation: Yes, the 6630M was a bit faster than the HD3000, partly because of the dedicated VRam.
On the other hand, 256MB VRAM were not that much even back then. And the 6630M wasn’t the fastest GPU to begin with. Thus you had little use from it for gaming or HD videos or whatever else you wanted to do on that mini.
Heck, the 6630M was only available as middle configuration, so if you needed CPU horsepower, you could not have a 6630M at the same time. Probably because of heat reasons.
Also - as with many dGPU’s in Apple products, the 6630M was infamous to die prematurely due to heat.
Consequently Apple did away with a separate GPU in the 2012 model - and imho rightfully so. Therefore I would not sign your claim of the 2011 mini w/ 6630M being a „pretty good“ machine. Too many cons for too little pros. Collector’s item maybe, but less useful than a proper 2012 model with a similarly capable iGPU and USB3 connectivity.