I have. The UK is as hard or possibly even harder now (since the brexit) as US. The rest of EU is not as hard but you need to weigh by pay difference and how many people actually want to immigrate, then it's not even close.
Essentially the UK requires you to speak English and have a job offer over 26k GBP in a skilled role where 'Skilled' expects the skills needed are that of an 18 year old school leaver, or less skill requirements if it's a role with a shortage, or less money if you have an advanced degree. That's pretty open IMO.
My recollection is UK immigration required you to pass some sort of UK version of TOEFL. US only has an official "language test" during naturalization and it's basically just one question that immigration officer asks you. Quite a difference in effort.
Tier 2 general visa is much easier than H1-B. Tier 2 ICT is near instant. You can then switch the latter to the former quite easily. And then it's 5 years flat to having ILR (which is a green card equivalent).
If you're Indian, you're waiting way longer than that in the US.
However, I think if you're not from India/China/Mexico, the constraint is that getting an H-1B is lottery-bound, and then you'll get the GC easily.
