Not currently an owner, but I have a WTB for one! These are the 4 I've previously owned, in order of their arrival and subsequent departure:
Sub750T Professional
Loved this at the time, pretty much my first "decent" watch too and if I remember the £800 felt a lot at the time! The bracelet feels light and adds to the vintage aesthetic with the polished beads of rice in the centre.
Sub750T GMT Sharkhunter
I was quite taken with this too. The dial looked relatively small with the inner GMT bezel which I loved playing with to change the appearance of the watch, not really needing to use a GMT function as intended. I remember being stopped by an Assistant when browsing in a jewellers in Dorset "hey is that a Diesel watch?". Imagine your pride and joy being mistaken for a fashion watch!
Sub1200T Searambler
Liked the starburst dial. Wore a bit like a Sea-Dweller (though not as comfortable) with a relatively tall profile to incorporate the HEV within the case side. Found the bracelet was quite thick and heavy in relation to the watch head - think it's the same bracelet as the GMT which is a larger watch and wears it better. If memory serves it originally had brushed beads of rice which wasn't as appealing as the polished on other models, but I stopped short of Cape Cod-ing them!
Sub300 Professional, 50th Anniversary
Oh to have loved and lost... Uber-Doxa for me, stupidly sold and seemingly hard to replace now. The font, lume colour and crown are all different to the current 300 version which I think is otherwise the same. This is how to do vintage-inspired lume without overdoing it! The retro font makes the current version look too bold and blocky. Would be delighted to find another...
Doxas seem disregarded by many, but they are definitely distinctive and hark back to the early dive watches with experimentation to the design and colours (look at the dwarf hour hand, sector dial, bold dial colours, beads of rice bracelet and distinctive bezel). Possibly a bit like Panerai - people tend to be split on their opinions of a watch originally designed for a different time and purpose. This was vintage-reproduction before it went mainstream :-)
Ant