What I find odd is that a ticket to Wigan gives you the choice if "Not Preston/Liverpool" at £23.10 for a return valid on any train, yet the Any Permitted is a whopping £32.00 (although if you are going for a day trip after 0930 it's a reasonable £24.90), yet a ticket to Preston is only £18.20 SOR / £16.80 SDR via Burnley (which I assume is what you want to do!).
So if it's a day trip the Wigan ticket may be best and that will allow you to do a circular route (via Preston one way).
Interestingly the Wigan SVR fare is valid on any train but Warrington SVR is restricted, barring arrivals into MAN before 0930 on the outward portion, so at peak times it is cheaper to buy an Off Peak to Wigan and stop 'short' at Warrington.