The 772 is approximately 209 feet 1 inch long, whereas the 773 is 242 feet 4 inches.

The -200 has smaller engines, but is a hair faster than the -300, with a cruise speed of about 490 knots, as opposed to only 482  knots in the -300.

Passenger capacity can vary, depending on the seating configuration, but while the -200 can carry a maximum of 440 pax, the -300 tops out at about 550.  (Crammed all together!  lol)

Hope this helps!