Your ds is obviously doing well on 5 hours a week to get multiple county times. I think there's a lot to think about before deciding whether to take the next step. My ds is 11 and has been squad swimming for 5 years. He has medalled at regionals. He trains 4 times a week (8 hours in total plus a bit of land training). Three are after school and the weekend one means he's getting up at 0415. The pressure is on to do more, but we're resisting it for now!
If your ds moves to the more competitive club and he doesn't do the amount of sessions they require from him, will he be asked to leave? Some competitive clubs 'cull' their squad swimmers on a regular basis to make room for others, ie if they're not doing enough squads or they're not achieving enough regional times. If that happens, how will your ds take it? Will his first club have him back?
Are you in it for the long term or the short term? There is nothing wrong with either approach, but a big increase in hours may bring short term success but at the risk of burning out. I've seen this happen a lot in our club - 10 years doing 12+ hours a week and achieving regional golds but quitting age 11 or 12. We have a massive drop out rate once secondary school starts - and we're not a very big or competitive club.
Many top swimmers (Adam Peaty, Ross Davenport) say they didn't do more than 4 or 5 squad swims a week until they hit puberty. They weren't wildly successful at age group swimming, but stayed with it long term and reaped the rewards.
A big thing to take into account is the move to senior school. My ds started year 7 this year together with the longer days and extra homework and extra-curricular activities this involves. That is one of the main reasons why we're not doing more than 4 squads a week. He is very small for his age and tires easily. Sometimes we drop an evening swim and do a before school one (ie getting up at 0445) and sometimes we do two swims in a day - before and after, but only when we absolutely have to.
It's easy to get caught up in the world of swimming. We still have 10 and 11 year old club swimmers swimming 12+ hours a week, plus intensive swimming courses in holidays and private lessons on technique on top of that. There's no way my ds can compete with that, but I know if we went down that route he would quit due to total exhaustion!
If you're going to move to the more competitive club, I'd be tempted to do it while your son is year 6 and he has less school pressure than at secondary. Good luck with whatever you decide! At least they're super-fit and are doing a sport they can keep up for the rest of their lives!