I think it depends on priorities. The Glock 30 (& the lighter, thinner G-36), Springfield XD45c, & even the S&W, are larger guns.
The XD45c, Glock 30 & 36, & S&W's are really compacts compared to the Taurus & Kahr. The Taurus Mil Pro PT145 & the new Kahr PM45 are sub-compacts compared to the rest.
Sprinfield Armory XD45c: 7.25" long, 1.25" wide, & 29.25 oz.
Glock 30: 6.77" long, 1.27" wide, & 23.99 oz.
Glock 36: 6.77" long, 1.13" wide, & 20.11 oz.
Taurus MilPro PT145: 6.125" long, 1.25" wide, & 22.2 oz.
Kahr PM45: 5.67" long, 1.01" wide, & 17.3 oz.
As far as personal experience, I have a Kahr PM9, Taurus MilPro PT145, & a Glock 36. All have been reliable. During break-in, I had a couple problems with the G-36 & PT145, but that was because of ammo issues. My Dept. gives me ammo for both practice & carry. Sometimes the practice ammo is old or of inferior quality, because of cost cutting. Thankfully, they don't skimp on duty ammo.
I use the PM9 more, but if I feel I need a .45, I carry the PT145. The PT145 is shorter than my old G-26, slightly wider & heavier, but it also holds 11 rounds of .45 compared to the 26's 11 rounds of 9mm.
The PM45 may have some teething problems, but like their PM9 & other models when new, they'll figure it out.
When the PM45 proves itself reliable, I think your two top choices for a "sub-compact" .45 will be between the PM45 & MilPro PT145. The PM45 is the lightest, shortest, & thinnest, but holds 6 rounds total. The PT145 is less than .5" longer, nearly .25" thicker, & nearly 5 oz. heavier, but holds 11 rounds total.