Does the 24/7 come with a 10 rd mag(my Commie state of NY doesn't trust me with more)?
How does the 24/7 compare with the PT111 and PT145?
Is the grip on the 24/7 compact noticibly longer than the other two?
RE 10 round mag - I believe Taurus has a separate part number for the guns shipping with 10-round mags, so yes, theoretically.
RE How they compare with the PT111/PT145 - as I understand it, the 24/7 differs in having the 'second strike' functionality - if a round fails to go off, the 24/7 reverts to DA mode to allow a restrike of the primer (and according to their research, better than 80% of the time, a second primer strike will allow a round to fire). Also, the 24/7 in the 9mm and 40SW sizes has the 'ribber' grip - I really like that feature; the ribs of the rubber-like grip allow for a positive, a hand-fitting hold.
RE Grip length: not particularly longer than the other two (and by the way, the Taurus web site gives the WRONG dimensions for some of the models; in particular the compact model, which implies that the grip is much longer than it really is.
Other than these differences, everything else will be very similiar.
Third generation Milleniums offer second strike capability, I know, and I think second generation milleniums/pros do as well.
Past those differences, I think the biggest difference is that Milleniums only come in 3.3" barrel varieties, whereas the 24/7 goes all the way up to 5" with the Long Slide and OSS variants. Both series of pistols should be very similar mechanically.