We do sublimation here. What DTG and Sublimation have in common is nearly zero setup penalty. You really can print that "just one shirt" that we are all asked to print when someone hears we do screen printing.
We started our sublimation program to do all-over printing. It's a bit finicky when you get to seams or deal with hoods, zippers, etc. Apparently most of the industry has accepted the occasional wrinkle as a reasonable trade-off. We also have a few lines of flat stock signage that look fantastic and are apparently selling well. You can sublimate 50/50 to a limited degree, but 100% poly always looks best.
requiring poly is a pretty major limitation for garments...I think there are some types of nylon you can use too. Also white garments only. I'm sure you could use other light color substrates, but we've never experimented with it.
I've been pushing for a DTG for years for our low volume custom orders which are increasingly rare and just as increasingly annoying to tie up the presses with when we have plenty of high volume stuff we'd much rather be printing. We've had demos of many units, they all have pros and cons but usually nothing too crazy.
I think DTG would be the way to go, personally. I'd definitely wear-n-wash test thoroughly as you narrow down which units you're interested in. Check the cost of pre-treating chemicals, ask other people with the unit how their experience is. You might be limited to pretty much just garments and have a more limited print area, but I think being able to throw a near photographic image onto any color substrate with minimal prep (manual pre-treat, buying pre-treated garments, or the initial pre-treat pass for machines that take care of that themselves) and having virtually zero worries about economies of scale for quantities, I think that is pretty awesome.
If you do a lot of promotional products then maybe sublimation might be more up your alley...you can get sub blanks for the most ridiculous things. iPhone cases, wood blocks, coffee mugs, key chains, tiles, street signs, blankets, towels, pillow cases, table runners, various throw-away promotional toys, etc. It's really ridiculous.