A 10.5 Blade III (haven't flown one yet) will get you going in as much wind as a 21.5m Titan. I use the 8.5m on land down to about 5 knots.
Blades have much more power per square metre than inflatables, or closed cell ram-airs, although the FS kites have a nice depower, which helps things when the wind picks up.
Watch the lofting though, with either kite. Even the 8.5 has almost carried me away on occasion.