I've done a ski season and they're really fun, a great experience. However, you get appalling pay and terrible living conditions. It is a good thing to do once, just to try though. You meet some really fantastic people. It depends how much you want this other job. If you're not really bothered about it, it will come out in the assessment centre and it will be a waste of your time. There is no harm in going to the assessment centre for experience and seeing if you get the job first. Once you have a concrete offer for both, it will be easier to decide I think. I personally don't think the ski season adds much to my CV since it was bar work and cleaning but I also don't regret doing it! Good luck!