The grip on the Bersa is definitely a bit thicker than the Glock, as you can see below (at its thickest, the Bersa was around 33mm to the Glock's 27mm, but the Bersa flares and tapers up near the top while the Glock is a block of wood all the way up).
However, since I have the extra backstrap on the Glock, it makes that grip fill my hand a bit better front to back. I would say I can release the magazine a bit more easily on the Glock, since the Gen 4 has the extended release and it sits wide and flat - from back to front it runs parallel to the side of the pistol, whereas the Bersa release is more button shaped and slants in toward the pistol as you near the front of its shape. Honestly, neither is difficult to use quickly, and on both pistols the magazines drop instantly and freely, with no grab. I have seven Bersa 10-round magazines, and there have been zero issues with any of them, including an easy load of all 10 rounds. With the three Glock mags that came with the pistol, I found it very difficult to load in the 10th round until they were broken in (I loaded them up and let them sit that way over several weeks).
The double-action on the Bersa is okay - I suppose if we were allowed to CCW it would come into play more, but at the range I load and rack it and pretty much always fire in single-action mode, and on the Bersa it feels really very nice indeed. The only thing I tend to find is in rapid-fire my fingertip starts to move down the trigger slightly (it's very smooth), and on reset you can feel the edge of the ball of your finger sometimes pinch a bit between the bottom edge of the trigger and the top surface of the trigger guard. I don't know if knurling would help but I may try a bit of grip tape and see how that works.
The other negative on the Bersa is accessories - I don't know what the holsters look like that Tactical has brought in, but the ones on the official website for the compact version look like they belong to another firearm altogether and just happened to sort of fit the Bersa so they went with it. The molded shape of the trigger guard on those holsters does not match the actual shape of the trigger guard on the pistol at all. Outside of that though, I think the Thunder Pro is an excellent value. I find it comfortable to hold, it's more accurate than I am by a fair measure, the trigger pull feels very crisp, field stripping is dead easy, controls are ambidextrous right out of the box (aside from magazine release, but that's a quick swap), and I think it's a good looking firearm.
Hope this helps you - let me know if you have any other questions.