Worked for quite a few year on the 737NG before lately switching to the A320 family, still rated on both.
I used several headsets, and had some mixed experiences with them.
Telex 850: Very lightweight, doesn't take up much room in your flightcase, good sound quality. Seems somewhat flimsy, but it never broke. Not enough noise protection for the 737 in my opinion, especially if you fly faster speeds (CI 45 and above).
Sennheiser HMEC 26: Very good noise protection, both active and passive if they sit correctly on your ears. Way too high clamp pressure though, at least with my rather big head. Since i wear glasses that leads to quite a headache after a few hours. On my private pair i had the talk through function, it is rather useless, i wouldn't spend any money on that. The connection to a music player is only very rarely useful, in europe there is usually too much radio noise going on for it to work nicely, on some quieter routes into eastern europe, africa and over the atlantic where we use datalink anyway, it is nice.
Bose QC-15: would be the best of the bunch, if it weren't for the dismal quality of the microphone. It produces a constant hissing background sound which can drive you nuts after some time. Apart from that it has great noise protection, is extremely comfortable even though the microphone is only on the left side. The downside is that it won't work if the battery dies, always carry spares and change them early.
Sennheiser 46: Without active noise reduction pretty much useless, it is our company provided headset on our airbus fleet, we usually only wear it for climb and descent, during cruise it is much better to work without a headset. Although i might spend some money on in-ear noise filters.
Plugs is mostly a company choice. I haven't seen a 737 with the XLR-5 connector and even on our airbus fleet only very few aircraft have it. The standard in my outfit is the usual two plug connector, so it is easy enough to use a normal headset.