There seem to be many questions asking 'is this or that suspension length ideal' or 'what bike for...?' that I thought I'd start a one looking at this a little differently. They're easy questions to answer once you've tried a few bikes (which is why I believe testing is so important) but for those asking the question I'm thinking it's more important to ask based on how you ride not where you ride.
For example. I really like this response on an earlier thread asking 'is 160mm too much for UK riding?';
People ride whatever floats their boat. I'm happy with that. For some people it's the speed of the descent that generates the most intensity of feeling. For others it's how close they are to the limit that matters. There's no single recipe for this
Is 160mm too much? Certainly not. But it would be if you like to pick your way down decents then put your head down and hike it back to the top as fast as possible.
Looking at the guys I ride with, we (mainly) fall into two camps; those for whom decents are just that, a down hill slope and the way to the bottom, then there the others for whom the decent is the focus, we (I'm in this camp) like to pick the best ones and once we hit the bottom we're quite happy plodding back to the top.
If you know the way you like to ride, or want to ride, the type of bike and amount of suspension (or lack off) you should buy becomes a much easier question to answer.
Personally I love hammering along single track, lifting and dropping my reverb to free the bike beneath me as the trail requires, when the trail points down it's about how fast I can go and where I can jump. That's my passion for riding and that's why I bought a 140mm FS, I wanted a bike that made small rocks and roots less of a hazard so I could ride faster and pick what I see as the 'fun' line. When I get to the bottom I often think it would be nice to have a HT 29r to ride back to the top, but only because it would be a little easier. Would I swap, not on your life...
Sorry for the essay, I seem to have plenty of time tonight...