Good things about fast boats for your MM Husband- (Late 80s early 90s info be careful)
1. ELTs on fastboats sometimes get double the workload when compared to a normal MM due to overzealous MM div LPO ("He's a mechanic first ELT second and that is how it is"!)
2. Fastboats will probably do more interesting things, like liberty ports and more interesting boat assignments. You could fly out and meet him if the conditions are right. I took a weeks leave in Italy and traveled across Europe by boat and railway to meet my brother in Gemany (Army).
3. Like someone else said, it isn't supposed to be "as good" anymore on boomers.
4. It really does depend on the commander/higher ranking officers and chiefs. You can have a great fastboat due to the people in charge. that's why I got out (one of many reasons), people who may suck have way to much control over you life, there is no rhyme or reason. So even though he is going to what some would consider the hardest assignment, really it depends on how good the people over you are.
5. If the fastboat needs upkeep you could end up in port for awhile, like years, but this could be good or bad. Sometimes it isn't fun at all, but he should get to see you at least 5 nights a week depending on duty schedule. It might only be for 8 hours though (worst case).

6. He gets to be a real mechanic. Not saying all ELTs were bad mechanics, and plenty of ELTs really got into it, but you will be put in more of a position to do real mechanical stuff. Isn't it fun to try to fix an evaporator? This could be bad or good depending on his aptitudes/preferences.
7. As an ELT he might have been stuck as only one of 2 ELTs on the boat (this happened to me more than once) in port. That means you spend every other day on board for 24 hours. And if something happens to the other ELT (medical etc) you could even be port and report until somebody figures it out!
8. You can go to an R-5 and get Radcon Training (the RC in CRC) if you really want it. Especially if your fast attack sucks and he wants to try something else ASAP, R-5 used to qualify as neutral duty so it was far easier to get.
9. It is easier to blend in as an MM, so if he isn't a hot runner but is decent at his job, he might meld better with the crew. Low number of ELTs per boat and spotlightish kinds of jobs make it harder to blend in as an ELT.
10. There are a couple of cool schools MMs used to be able to go to, it was harder to get these schools as an ELT on my boat.
11. ELTs usually do "baby radcon". If he is interested in getting into RADCON, the stuff at R-5 will be more real deal type of radcon.
12. HE still may be able to get ELT. I don't recommend it, but if you 2 decide to stay in, he could get sent back to prototype and get ELT I think. Have him ask about this.
13. People on fastboats can become really good at stuff because you are all they have to do things, so you might have more opportunity to "be the man" at something. I got to go to dive school because no one else could pass the test!! Or like QA stud or something like that, which could land him a good job outside of the NAVY possibly.
14. There is a way to come out and qualify for CRC jobs on the outside. Most commercial plants do not use a combined C/RC tech but a few do. He could go to R-5, and while he is in the Navy get a Chemistry degree. This would be very difficult for most situations, but one easier way to do it is for him to get as many credits as he can while in the Navy, then use the GI Bill to finish it up when he gets out. A great alternative plan if he gets out during a bad time in the Economy. I don't know how bad he wants to be CRC, I'm sure he will reevaluate when he has some "time on the pond".