I agree with a lot of the above. Firstly that there are no "unsafe regulators" - there are some that I don't especially like, but I'm pretty confident that any well-maintained reg that I use will deliver air when I need it, even if it looks prehistoric or gaudy. For recreational diving, the rest is down to personal preference and budget.
Think of a regulator like a car or motorcycle engine - they are designed and built to well established engineering standards, within a set plus or minus deviation from the perfect product, and will therefore get you from A to B without any unnecessary drama, assuming you use that engine within the limits for which it was designed. If you look at production motorcycle racing such as the World Superbike Series - they use exactly the same engine that's in the sportsbike you can buy from any high street bike store... but it's blueprinted and tweaked to conform more exactly to the ideal design.
Regulators are a bit like that. They are not - generally speaking - especially complicated pieces of equipment. Any basic set of regulators will do the job just fine, but if you can afford to pay the premium for that extra bit of precision engineering to make the breathing experience just that little bit smoother and without the rattles and whistles common to many basic regulators, then by all means go for it. Barring completely unpredictable and spectacular failure, rather like engines, they are not going to let you down.
It has to be said, however, that - exactly like motor vehicles - some manufacturers do have a greater or lesser market presence depending on location worldwide. As an example, Oceanic have no presence at all in my current location - so given that I work here, it makes no sense for me to own an Oceanic regulator, because I can't buy spare parts and service kits here. So - if you have an Oceanic reg and dive here and are worried about potential breakdown, then it would make sense to buy a service kit before traveling, just in case. Rather like engines, they might have differently shaped components but their basic operation is fairly similar. Balanced or unbalanced, 2-stroke or 4-stroke,
this bit slides back and forth,
that bit opens and closes, and the spring in the middle goes *boing*. Any decent mechanic should be able to look at either design and work out how to fix it.
There are liability issues here - just like car manufacturers insist that you should only get your vehicle serviced by a mechanic trained by their own company otherwise your warranty is invalidated - so do regulator manufacturers insist on the same. I personally think this is crap, because from my own experience, I learned to overhaul my motorcycle - a Suzuki GSX-R 750 - because I was sick of incompetent, "manufacturer trained" mechanics charging me lots of money for nothing, and so when a friend asked me to service his Honda CBR600F, I didn't even have to think about what I was doing, because the engine operates on exactly the same principles, it just looks slightly different. What's the difference between Haagen Daaz and Ben 'n' Jerry's ice cream? Pretty much nothing except the presentation.
Yes, it's true that you are not going to find spare parts for your regulator of choice in all parts of the world, but this applies mostly to the internals of the first and second stages. O-rings are o-rings and for sure there is one that fits available locally wherever you are, but a high-pressure seat is generally uniquely tailored to the regulator you own - or at least the brand. When it comes to metric and imperial differences - most centres I have experience with carry allen-keys (hex wrenches whatever you want to call them) of both flavours. If you're in doubt, your own personal set will cost next to nothing. For nuts and bolts: all hail the adjustable spanner!
Some regulator sets have proprietary screw threads for their LP and HP hoses - that is to say, only hoses from that manufacturer will fit. I've encountered this a few times but I'm hard pressed to remember which manufacturer that was. This annoys me because hoses are just hoses and it's like saying that you can only fit Ford tyres to a Ford car because we've designed our wheels to ensure that nobody else's tyres will fit on our Ford wheels. This is not true of Ford cars, by the way, in case anybody wants to sue me now - it was just the first name that came to mind!
So - buy what you like but carry some spares if you feel you might not be supported by the manufacturer overseas. If there's a random and unresolvable failure on holiday, then you will probably find a rental set of regs available. This might not be to your liking, just as riding a rental scooter is nowhere near as cool as hammering your sportsbike through twisted country lanes, but it still gets you where you want to go, and can be a huge amount of fun if you lower your expectations a little
Cheers
C.