Are you actually in Thailand? That could significantly influence the availability of boats, and the ones that might be recommended for you.
I can appreciate why a big trampoline would be nice; I've been out on a few cats and they do create a spacious deck, and some even have a comfortable lounge area. My problem with cats is that, until you get into the bigger ones (36 is probably the minimum), the hulls really aren't wide enough to give you a lot of elbow room down below. I know you mentioned that you're OK with "roughing it", but it is nice to be able to actually walk past another person without both of you having to turn sideways. If you're planning on using this as a for-hire boat for day sailing, then I think something in the 36' range would be fine. But if you're overnighting, and if you really expect passengers to want to come back, I think something in that range just isn't going to be that comfortable. Now, my opinions are based on walking aboard cats at boat shows, so take them with a grain of salt. Someone like ChucklesR is really the kind of person you want to chime in here, because he sailed a Gemini for several years.
Cats are also great because they don't heel like a monohull, and they are faster in light winds than their monohull cousins. But monos have other advantages, including elbow room. They don't have the trampoline, but you have to be careful what you put on the trampoline; a bad rip can mean a very expensive repair. The same is true for fiberglass, but different.
I'd encourage you to go for rides on other peoples' boats before you buy. You might just be surprised how well a mono might fit your needs. Plus, its much easier to find a slip for a boat with a 10-12' beam than for a boat with a 25+' beam. Monos are also more plentiful, and less expensive, than most cats.
So, now, stepping down from my soap box...
As a practical matter, I don't know too much about the MacGregor cats (or most boats, for that matter...I'm new to this too, though I DO tend to research things a bit). I have seen them in listings, and thought they looked interesting. How long ago did the company stop making them?
FYI, it was announced earlier this year that MacGregor is closing shop. The founder's daughter is starting a new company, but the Mac's won't be made any more. Now, there are THOUSANDS of Macs out there, so you'll likely still find support for them for a long time, but it may be important to know that the factory won't be there any more.
From what I understand MacGregor was a pioneer in the production boat building space. Sure, Luhrs brought out the Hunter boats, and I think Catalina beat them, too. But they took things to a whole new level. They built boats for a price point - where else can you find a brand new sailboat for $30-50K? - and they found ways of meeting that price point. They built thousands of boats, and sold them to entry-level buyers. For most buyers, these were their first boats. So, that meant that the boats weren't always that well taken care of. Plus, the production processes and techniques used by MacGregor were designed to crank out boats. They weren't always the highest quality, and thus their owners really should have paid more attention to the care and maintenance of the boats. They also suffer from a lot of the same problems as other production boats of their era. If you just wander a marina and ask people about MacGregors, you'll find that most people will tell you that they stink. They know someone whose friend had one, and it sank. Or it had rotten decks. Or the mast fell down, or the rudder ripped off, or... But you'll have a harder time finding an actual owner who has had serious problems with his/her boat. Yes, there are bad MacGregors out there. There are bad Catalinas, bad Hunters, bad Pearsons, bad Island Packets, etc. And the sheer number of MacGregors, and especially the target market to whom the vast majority were sold, means that there are some out there that have been VERY poorly maintained. But you'll also find videos of people who took stock Mac monohulls out in 30-50kt winds off Southern California, and people who trailer them all over the country.
So, would I buy a MacGregor? Probably not. If I sailed a lot of lakes, I'd consider it. Or, if I never expected to leave Barnegat Bay or the upper Chesapeake, maybe. But there's enough nagging doubt in the back of my mind to have me concerned about having my family offshore in rough conditions in one. I also don't like the layout of the cabin on the 25's (the only ones I really investigated), nor do I care for the cockpit (it seems too tight to me). I do like the modern design, though.
So, I've given you a page-long response, but didn't address your question.