If Jet2 offers you a better lifestyle I would say go for it, take Jet2 and nail the command course in a years time, if your plan is to enter Jet2 as a captain I assume they operate out of a base you want or would offer you a better lifestyle than RYR.
I tend not to subscribe to these various rumours that the X airline command course is difficult, or you have to avoid such and such a training captain or you'll fail etc, you'll end up calling in sick for half of your checks if you subscribe to that sort of thinking, and generally try and go in with the attitude that they want you to pass and it is yours to fail. I can appreciate that much of it is luck of the draw, if you have a complicated problem come up whilst on the initial command line check or bad weather etc but that's the nature of the job I suppose.