Excellent comments, Adlerdriver
I've been there and done that regarding becoming a part-timer too soon. Fighters in the Guard/Reserve are a serious commitment which has gotten much more so since I left in the late '80's.
The C-5 is probably the easiest to get and stay proficient in along with the tankers. The C-17 and C-130 have a pretty decent balance of tactical (read: hand flying skills and thinking on your feet skills) and required commitment, still about 7 days a month as a part-timer once MR and with a 1,000 hours.
Like anything, you get out of it exactly what you put in. Fighters demand lots of "puttin' in" and one gets gets lots of flying and thinking skills. I have yet to meet a former fighter guy who could not be put into any flying environment and not excell--even CRM usually isn't an issue. Getting 3-5 other guys, in their own planes to do the task, whatever it is, takes CRM skill.
The Guard babies have had it pretty good in the past decade, lots of flying, good experience that generates proficiency and ability to upgrade. The next ten years, I cannot say, but joining won't be a big mistake.
GF