I wouldn't bother either unless you're diving in restricted spaces where the yoke (not yolk!) knob is an entanglement hazard. The DIN connection is not "much more reliable" because, as bubbletrouble pointed out, modern yoke connections are very reliable. They tend to get a bad rap because you see them on rental tanks all the time; and you do see a few knackered up valves with pretty crispy o-rings. But that's cause they're rentals, not yoke. (Except the o-rings which are easily replaced on the boat) If they used all DIN tanks at a resort like, for example, Cozumel, I'm sure you'd see some pretty scary threads in those valves, some knocked out of round, etc. and they would be about the same trouble as the current yoke tanks are, maybe more because you'd be able to screw up (literally..) your reg's DIN fitting. As it stands, no matter how bad a rental yoke valve is, it won't damage your reg.
If you're dying to use your tanks as DIN, why not use this as a perfect excuse to buy a new regulator? I've succumbed for far less of a legitimate reason, and you could explain it away by saying that either A)you don't want to alter your current regs (okay, that's pretty dumb) or B) The cost of replacing the yoke is almost half the cost of a new 1st stage. (That could be sort-of true!)
