For a small CCW 10+1 45ACP IMHO you can't do better than the PT145 unless you are willing to spend 2X more $$$.
Compare the size of PT145 to a Kimber Ultra Ten II -- at least the PT145 mags worked out of the box, Kimber's didn't! PT145 mags are also cheaper and easier to find.
You can get a little smaller with a Para Ord P10 Warthog, but again about 2X the cost, and many folks can't handle "two finger grip" on the Warthog. My P10 has a rather mediocre trigger as far as 1911s go, Warthogs might be better (or worse
Major PT145 weakness IMHO is the DAO trigger. I rate it a bit better than a stock Glock trigger, quite a bit worse than a Kahr, but none are in the same league as the Kimber Cocked'N'Locked SA trigger. But unlike Glock and Kahr, the PT145 is true DA with a second strike capability. IMHO Kel-Tec P11 trigger is worst of the lot by a good margin.
Be wary of any used Millenium unless you can verify its recent production as there were some serious initial problems and the triggers seem much improved recently compared to guns made a few years ago.
Is the XD available in 45ACP? If you can sacrifice the 45ACP and 10+1 features look to Kahr PM40 for smallest and lighest or Kahr MK40 for smallest with less recoil but more weight -- steel frame vs. plastic.
The recoil of 45ACP is IMHO way over rated. No where near as "snappy" as 9mm or .40 S&W.
--wally.