There are plenty of other beaches to sail on the Causeway Coast, subtle nuances in wind and swell direction can make any one of them king on their day. Downhill, further east from Benone, is an option as well as Castlerock which can offer bigger waves if the swell is small. Across the river Bann is National Trust run Portstewart Strand offering similar conditions and moving further east along the north coast towards the Giant’s Causeway is Whiterocks, a punchy beach break with strong rips, so small swells and experts only. There are a few other spots further east but these are pretty hard to access these days and to be honest are better for surfing than windsurfing.
On the subject of surfing, make sure to pack a surfboard or SUP as the north coast is surf city! It is not unusual to see 30-40 surfers out at East Strand in Portrush on a winter weekend and the town has two surf shops (www.troggs.com and www.woodiessurfshop.co.uk ) which both do surf reports on their social media.