I was there in January. Weather is good, although you can experience temporary (heavy) showers. From Maho Beach, you can always find a good sun orientation. Watch the time tables, as some heavies do not come daily. AF
A340 does, but not Corsair B747 nor KLM.
Whatever the camera brand, lenses like 24-70 for the heavies and 70-200 for the smaller airplanes is usually sufficient. A wider angle (14mm or below or even fisheye) is usefull for special effects from the beach;