I own both guns
By far the Bersa Thunder Ultra-Compact 45 is more reliable and a better shooting gun. The gun sights up very quickly and feels good in your hand. I am more accurate with it from 10' out to 50' than I am the Taurus PT145 or my Springfield XD .45 Tactical. (I've worn out my Springfield so that may not be a good comparison)
This is the first gun I have ever owned that is fully ambidexterous and the safety and slide release are very accessible with your thumb and are extended by design. The gun extracts from my holsters cleanly due to the contoured safety and slide release being blended and fitted tightly to the frame. The grip is anatomically designed which naturally guides your finger and thumb into the right places. The extended heel plate on the magazine gives a place rest the pinky.
The single action trigger on this gun is very predictable and breaks cleanly. The double action pull is a little on the heavy side, but again, it breaks predictably at the same point each time.
The 7 round capacity and weight (27 ounces) of the gun are the only drawbacks. Also, the rear hammer spur could have been extended a little. The hammer has bitten me a few times, but no big deal. Thats what I get for having a fatty hand web.
By far this is the best SA/DA compact .45 I've ever seen. Period.
The Taurus Millenium Pro: I had a bad experience with this gun when I first bought it. The magazines would drop out of the well whe firing! I had to send it back to Taurus twice before they fixed it correctly.
That being said, it's not a bad gun, but it does shoot low. Now keep in mind that it comes with Hiene Straight 8 sights and that may be part of the issue. The other part is probably the trigger. The trigger is fairly smooth, but the trigger pull is long and stiff (9.5 lbs.).
If you're looking for a big-bore ankle gun, this is the best one I've seen and carried. It has a fairly low profile. Everything is fitted tightly to the frame and does not protrude to snag on anything. It is light and holds 10 rounds of .45 ACP.