I'm a US Marine and even I have to admit I’ve always wanted to be a Royal Marine, but I stayed in the US so long that I decided to go in a different direction. You have to have lived in the UK for the last five years and be younger than 26 to be an officer so. I went to college in the US -that ended that dream. In the US Marines I found great challenges and just as much opportunity to be the best -it’s just everyone doesn’t go for that as there is also plenty more opportunity to take it slow.
From my new perspective I wouldn't say the Royal Marines are any better than the US Marines. Royal Marine Commandos are trained and used like US Marine reconnaissance men or MARSOC guys. The Royal Marines are a rapid deployment force. If you compared the Royal Marines with a comparable US Marines unit or Navy Special Warfare Combatant-craft Crewmen, I think the branches are about on par with one another. But you can’t go comparing the two forces as a whole because the US Marines have gained much more "slack" as they evolved from their Royal Marines mold.
The organizations have a different philosophy. The US Marine Corps applies the Royal Marine philosophy to only some of its men/women -well in this case, men. Every Royal Marine cook is a “commando” underneath. Every Marine Corps mechanic is just a “rifleman” underneath. Every US Marine that is trained as a “commando” is a full-time commando. Comparing entire organizations just doesn’t work
Royal Marines definitely have a longer and more grueling boot camp (which is why I wanted to go in the first place). It's the longest boot on earth.
Some US Marines argue that the two aren’t comparable because the Royal Marines are used as the United Kingdom’s SEAL operators. No, this is not true. The United Kingdoms’s SEAL-like operators are the SBS (Special Boat Service) and it is inappropriate to suggest that the Royals are that far from a fair comparison.
The US Marines have lower entry-level expectations because there are many more support occupations and it’s a much larger force. US Marines who perform a “commando” role (parachuting, airborne rappelling or fast-roping, amphibious landings, counter-terrorism, reconnaissance, sabotage, and other clandestine tasks) are comparable to our Royal Marine brethren. We train very hard for very long.
As an addendum to the comment above mine, there are about 175,000 enlisted US Marines (excluding officers and reserves). There are about 7,500 Royal Marine Commandos. USMC's MARSOC has 2,500 operators and officers. And there are 4 USMC recon battalions of about 500 men each (2000 total). When you consider that some of those Royal Marines are helicopter pilots and support, that means that both forces have about the same amount of commando-type operators (around 5,000) and I believe these men are on par with one-another.
Former UK dual Citizen
Current Lt USMC