Every time I check back on this thread, I build up a little more incentive and motivation to set up a reef tank myself. I really like the contrast of the FW planted vs SW reef. I've always wanted to venture into SW but ignorantly told myself that it was more expensive, difficult, and required lots of maintenance. However, you said that the SW tank sustains itself? What's the maintenance like? The reason I ask, is I can feel the labor of love of trimming the plants, cleaning the filter, tubes, pipes, water change, siphoning poop, and wiping algae off the glass in a FW tank, so if the SW is actually better maintenance wise....I might just pull the darn trigger!
I'd say I do 3-4x more work on my FW than my SW. But hasn't always been the case (like in the first month or two of the reef) All I do in my SW tank is dump in RO water once a week when it evaporates and vacuum. Vacuum is super easy since its bare bottom... I just cut a 2 liter and stuffed it with filter media and I sit it in the sump and siphon water from the tank into it, which filters out all the poo and debris and returns that water into the sump which goes back to the tank... so no WCs required to do this. Wipe down the glass once a week with the magfloat too. Thats about it.
I call it a budget reef, lol. I got by doing things a lot cheaper than most people do. Cheap skimmer (sca301 - works amazing) got an old used wet/dry and pump for filtration for 25$, cheap tank since its just normal 20L with rim removed, got a steal on the PAR38 at 37$ on ebay and built my other fixture for under 50$. The live rock and coral were the most expensive thing, but perks of a tank this small is you dont need as much. I've never sat down and added it up, but broken down over time it wasnt too bad. You can EASILY spend as much as I did doing a larger FW planted by the time you buy hundreds and hundreds of dollars in substrate, ADA stones and rare plants and mosses.
Not saying SW is cheap, but I didn't go all out and get all this insanely priced stuff like some do. Every tank is different though, just gotta convince yourself to take that leap.
Words of advice - When you think you have a big enough filter - go bigger ( mines rated for a 125g tank), RO water is an absolute must, get a protein skimmer, get good quality live rock and plenty of it to start out with (do not get dry base rock or you will end up regretting it like my gf did in her tank covered in hair algae) and dont get many fish.
Good luck if you take the leap! I love both.