Eddie
This discussion hasn't been covered in a while and like the points vs. electronic ignition subject has divergent points of view. Here's my take for what it's worth:
Original Amals; usually real bad shape by now on most bikes unless they've been re-sleeved. Figure at least $100 US per carb to set them right, which should give 20k mi or more service before needing any serious attention. Keeping them balanced is a little bit of a pain, but the plusses are; good top end power, look original, least trouble since nothing needs to be adapted like air cleaners or cables. Amal re-pops seem to be getting bad reviews for quality, concensus says stick with the originals if you can.
Single carb; Usually a kit, they cost about $250 US for a 32 mm Mikuni with everything you need to make the swap. I've seen other kits that use a single Amal or larger Mikunis, but the most popular seems to be the 32 mm set up. The blokes (can I use this not being from down under?) that have them seem to think they're the way to go but all admit to a drop off in top end power as a trade for the convenience of not having to fiddle with the balancing. I don't recall what the durability is vs the Amals, maybe some of the other members can advise on that. Generally once set up they tend to be trouble free.
Thats about it in a nutshell, hope it helps and welcome to the forum.
Scooter