Reels are useful things - they can be used as guidelines, to stop you getting lost. They can be buddy lines, to ensure you don't loose your buddy in low vis. And they keep you connected to your SMB. As with most important bits of kit, I carry two.
My main reel is a large McMahon. It's bulky, but after using little pocket reels a few times, I'm happy to take the bulk in return for a decent winder. When I wanted to see how easy it was to use, I took it to the pool, fixed it to one end, and then pulled myself the full length of the pool using only the reel winder for movement. It was no effort at all.
The only problem I've had with it is that the release lever can be pulled so far down that it rubs against the spool. Drilling a small hold and putting in a SS bolt stopped that being a problem.
My backup reel is a Halcyon spool, which is tiny enough it can happily live in my drysuit pocket with no problems. I'd only use it as a last resort, because of its small size, but I happily trust it to work if I ever do need it.
There was a time when I left my large reel connected to my main dSMB. I decided against this in the end, because it meant I couldn't use the reel as anything BUT a dSMB reel. By having them separate, it's easy to clip them together, and I can still use the reel for other things if I should so desire. Besides, it's easier to stow if it doesn't have the SMB stuffed on its handle.
