OK, say one does want to travel someplace with AL80s and they want to SM
I'm a bit late to this. I alwasy take my SM rig on vacation because I despise a single AL 80 BM.
I also have am X-Deep Stealth 2.0 Tech.
@rick00001967 made some very good points on the first page which I'll add too
My rig is specifically set up for travel, thus my slings are permanently fitted with cambands, rather than metal worm drive bands
Since the vast majority of my diving is from boats sometimes into choppy seas, but nearly always on to sites that have significant current, my rig is configured appropriately. I choose between the compromise that ring bungees give (regarding perfect tanks position) vs day to day usability on boats
Instead of loop bungees I have ring bungees, which means I can jump or roll with both cylinders attached. Here at home that giant stride may also be with a scooter as well.
If I need be make a direct descent because of teh current I can (and do). Sorting cylinders at the surface is a no go for the type of diving I like. If required I can also get back onto the boat with both cylinders still attached, but its just as easy in calm seas to clean up at teh stop and hand off my tanks at the surface. I prefer to have as much flexibility as possible
I've never yet had any issued from shops supplying all the tanks I want (I generally switch both cylinders even though theres plenty of gas remaining) but I do take my transfill whip in case I'm only able to change 1 and then equalise the pressure between them
Frankly I'd rather take a SM rig around the world then having the faff of travelling with a pony, but I appreciate other people have a different view