I also own a T3EX and still love it dearly even though most of the labelling has peeled off and it needs a new replacement battery!
It does have 4 midi outs but these are set up as 2x2 outs- ie- 2 outs share 16 channels and the other 2 outs share another set of 16 channels giving 32 midi channels total- this is very handy for hooking up extra gear to use with the T3 without requiring and extra patchbay or using midi thru etc.
The T series are built very solidly- much better than the newer Korg units like the X and N series.
The 8 track sequencer is like the M1's design but also contains 200 patterns and has a 50,000 note capacity and space for up to 20 songs (memory permitting).
The 3.5 inch floppy drive accepts hi density disks only not double density like the newer O, X and N series. You can use the drive to store up to 1 MB of sample ram data plus one bank of program/combination/sequencer data or set it up to store 4 different banks of data without the sampled sounds.
The user interface is really excellent for a keyboard of that time thanks to the large screen and the sounds hold up very well even today. The biggest limitation with the T series synthesis architecture (and all the Korg synths from the M1 right up to the N series) is the very weak sounding digital lowpass filter without resonance. I did a fairly respectable resonance simulation using extreme flanger settings but don't expect squelchy synth sweeps etc from these keyboards.
All 3 boards are the same except for the keyboard length.
You will not regret purchasing a T series keyboard! I will never get rid of mine
.