I acquired them in that order :
A4 (Q3 '13 : first synth ever) -> OT (Q3 '13) -> MD (Q1 '14) -> AR (Q4 '14).

And prefer them in that order :
AR+A4 -> OT -> MD.

But that may be because I just got my AR and love it’s immediacy and the organic feeling of scenes and perf modes.

AR and A4 are an amazing combo !
I rarely use the AR without the A4 (mostly for melodies, basslines and pads/FX.)

Although the OT is only third for the moment, I use it all the time, if only as a mixer, MIDI sequencer, FX processor (including cueing to external FX) and a loop sampler (from other synths like Monotribe and Shruthi-1.)
It’s an amazing box but I’m still new to music production and am more comfortable with boxes which generate their own sounds than with samplers of that depth. Need still more practice with it…
I’m having loads of fun with the AR samples, though.

MD got a lot of love until AR arrived… love that analog punchy sound more than the more glitchy digital nature of the MDUW+ for the moment. That will probably change once I got enough practice with AR, then I’ll try to combine them both.

Desert Island box ? Don’t make me choose, please !
For now it’d probably be the AR, but once the OT will be mastered…