If money were no object, London would be the best that I know of. Montreal is best in Canada in terms of price, general attractiveness and service levels of the girls. Toronto is a close second. I find it's far easier to get laid in Montreal for free though, if you're relatively attractive and speak French, so to some extent the high-quality of sp's there is almost redundant. I wish I knew what's in the water in Quebec that makes Francophone women so hot and uninhibited.
I have a different opinion about the hobbying scene in London from my personal experience. When I was in London last year, I partook in this hobby quite a lot. In my opinion, hobbying in Toronto is a lot better than in London for the following reasons:
1. Agencies and indies in Toronto usually have really nice incall locations (ie in modern highrises or posh hotels and everything looks clean and new). While in London, unless the SP stays at a nice hotel, incall locations usually don't look as nice as their counterparts in Toronto. Incidentally, I've heard people seeing an SP in a shed outside a house in London.
2. In terms of services and looks, I would say SPs in Toronto dominate their counterparts in London. For instance, we have so many gems in Toronto (Anastasia and Missy to name a few). In London, you are very unlike to find SPs that are look as attractive as our gems. Also, service-wise, SPs in Toronto are better as well. For instance, CIM is usually extra (if it's provided at all) in London. Here in Toronto, if an SP does CIM, it's usually included in the rate. Incidentally, I (and many other "punters") found that Romanian SPs in the UK in general are the most restrictive and offer terrible services. And a good proportion of SPs in the UK are Romanian.
3. Attitudes: Again, SPs in Toronto dominate their counterparts in London. Most girls in Toronto are pretty laid-back and friendly. In London, it really depends on the background of the SPs. At least for me personally, I fount that Polish SPs are the most friendly and then the local British SPs (although they are a minority in the business) come in second. Hungarian SPs are pretty nice too. If I say anything more about SPs from other places, you will probably call me a racist. So let's just leave it at this.
4. Prices: The rates in Toronto are a lot more reasonable than those in London for sure. However, if you work in the UK, the real costs would be about the same, but the experience on average in Toronto is a lot better. You get more bang for you buck.
5. This point is actually in favour of the UK hobbying scene. If you ever find a wild British SP in London, she will be a lot wilder than you would expect (I am talking about CIM, swallowing, rimming and many other services all in one session). But these SPs are very rare. I've seen two such SPs back in London (out of too many to remember). One has sadly retired, and the other only tours London once every other month or so. And they are both very young and attractive. I have yet to encounter such SPs in Toronto (or at least my mileage is not as good here).
6. In terms of diversity/variety, Toronto beats London every single day. In London, most SPs are from Eastern Europe (mostly from Romania, Poland, and Hungary). Local British SPs account only for less than 10% (my own estimation, I doubt there's a statistics anywhere on this matter). There aren't that many Asian SPs in London. While in Toronto, you can find SPs of all sorts of backgrounds.
I can't really comment on hobbying in Amsterdam, but I heard it's a lot worse than in the UK.
I can confirm that hobbying in Toronto is a lot better than hobbying in Vancouver or the US. Haven't tried Montreal yet, but I'd say that Toronto is probably one of the top places on Earth for this hobby.
Another place that I think could be better than Toronto is Germany because of its FKK establishments.