I'm sure there's lots of good and bad experiences of Optimas detailed out there on the web, but the HUGE stack of dead ones outside Frog's Island a few years ago told it's own story. IIRC they couldn't get rid of them as they were warranty claims.
Leisure batteries are less suitable for winching than normal starting batteries, if you want the best battery for winching then go for traction batteries but get ready to feel some financial pain. A hydraulic winch with a PTO driven pump would be better, Ian might get around to prototyping this arrangement one day;-)
All the best,
Toby