My personal experience is only with the h16... and I sail solo, most of the time. I'm 6'1" 260. I just bought it last year and have been out 10 times total.. 8 of them solo. I sailed on multiple gusty days, 20-25... and it was a handful to sail it solo on those days, but still very fun! You just get tired after awhile.
I found 10-15 kt winds to be awesome for solo'ing! I could practice flying a hull, etc. Gusty days make it more challenging because you have to be on your toes to let out some line.
As for righting... I have yet to capsize it.. but I will do it next season for sure... because I need to learn how difficult it is to right by myself but my boss, who gave me some instruction said he could right his prindle 18 by himself and he only weighed 200lbs. when he had it.
I personally have no experience with other hobies... but my boss loved his prindle 18 and said he sailed it solo many times.. but I believe he said it's way easier with a crewmate. I've seen the h18 in comparison to my h16 and I bet I could probably handle it solo and probably even right it, but I'm a big guy... I'm sticking with the 16.. it's tried and true... and the thing about spare parts is a big factor!
As for investment... I paid $750 for my '82 h16 with trailer from a friend. It hadn't been sailed in 10 years. Needed a new tramp and new lines. Sails were in good shape! I probably spent $500 or so on upgrades/replacement parts and now I'm all set for years to come. I didn't replace the rigging, but I may next year just to be safe. Nobody wants to de-mast, but honestly, the wires look good to me...