Rainer T , Jun 27, 2008; 03:49 p.m.
-- "Tamron 24-75mm f/2.8"
No such lens. Its a 28-75/2.8
1+2 are both excellent lenses. 1 can only be used on crop bodies, 2 can be used of FF as well. If this shall be a good alround lens, #1 is a good choice. If it shall be your portrait lens, #2 seems the better choice.
3 is an excellent portrait lens. This and the 50/1.8 is all you really need for portraits.
4 has a good reputation as a general purpose tele lens, but not exactly for portrait. I have no personal experience with it.