The PT111 is part of the PT1XX family - all very similar in form and function - I own the PT140 (40S&W) and the 24/7c (9mm) -
As you can see they are very close in size, the 24/7 being slightly more bulky. The 24/7 is just slightly heavier. I *think* the bore axis is slightly lower on the 24/7 - yielding slightly less recoil. I don't notice the difference much, but I'm pretty used to 40S&W in compacts.
The 24/7 ships with a standard compact magazine and a 17-round magazine with an extension sleeve to bridge the gap. Works great and for range work it saves reload time. Or carry it that way, though it makes the grip a little long for my taste.
Both are good solid guns - good solid value for money. The 24/7 is a somewhat newer design, but there's nothing wrong with the PT design.
I believe that you'll pay a little less for the PT111, but either should serve you well.
Oh, forgot to mention the 'ribber' grips on the 24/7 - a very comfortable grip.
Go to
www.taurususa.com for specs. They don't have the 24/7c images up yet, but the specs are there to read.