Hi Oliverf - well the main difference between Gecko and Blast, as outlined above, is that the Geckos are quite a bit wider in the centre in a similar volume to the Blast - interesting size for you would be the Gecko 122 at 77cm, so for example this is the same width as the Blast 145, 23L bigger, just to compare. The Gecko´s are pretty much designed exactly for what you are looking for - a rider coming from bigger boards, wanting to perfect the basic gybing/planing skills, but on a smaller size board. The tails on the Geckos and fin sizes are made especially narrower/smaller, so that they are easy to gybe, whilst the extra centre width really helps to keep planing through the gybes. The Gecko is in no way a slow board, but has better control than the Blast.
When we do cross testing, there is actually only a very slight speed advantage on the Blast, even though most riders "feel" a bigger speed difference, as it rides more free over the water. So I would really reccomend the 122 or the winds you mention and your current skill level. You could go for the 110 Gecko too, it´s still fairly wide at 72cm and certainly not an issue for the wind strengths you mention, but I imagine living in Dubai, that a slightly bigger board is not a bad idea for the in-between days/your current skill level? hope that helps!