Personally, I’d go for the 10m Razor/ 15m Flite to cover a broader wind range. This is what I do when travelling. There is an appreciable difference between the 12m and 15m. And as an advanced rider, you should be able to handle the large spread between the 10 and 15m. A couple extra knots on the low end can make a big difference on those light days! But what’s you’re style? Surf? Freestyle?
What’s the difference between the 12m Razor and 15m Flite? I won’t get into the obvious differences. I’d say the high end of the 12m is better than the high end of the 15m, relatively speaking. The 12m is better in gusty conditions. In general, I find all large kites handle extremely gusty conditions poorly compared to their smaller counter parts. I guess it’s just mathematics, a 10 knot gust on a 5m kite vs 15m ......
I guess I’m one of those lucky guys who has one of everything (including a SP2 19m/15m- which I also never use) and rarely has to make a really tough decision. But, I have learned over the years that in gusty conditions a smaller (12m) kite and bigger board works a lot better than the opposite. So, it depends on how gusty the conditions are on average. Big kites will just drag you downwind in the gusts.
Having said all this the 15m Flite is my light wind kite of choice (over the SP 2 15m/19m, CAb. Crossbow 16m, Waiman 14m, etc.) for it’s direct handling/ quick turning/ and extreme light wind ability. Hey, if you can ride powered up on a surfboard and there’s no white caps that ain’t half bad!