To me, maps are simply not optional, period.

I know that all Swiss official publications recommend the 1:25,000 maps, but I never use them. They contain more detail than I need, and it takes four of them to cover what a single 1:50,000 map covers.

Of the 1:50,000 maps the ones I use are the hiking maps (T series): Swiss Hiking Maps 1:50 000. These highlight the trails that the Swiss Hiking Federation considers "official", making them easier to see. Of course, they make it easy to completely ignore non-official trails, many of which are very rewarding!

The Swiss hiking trail system is a living, dynamic system, with trails added and others abandoned frequently. Many of the commercial maps are not updated regularly, and show erroneous information. So stick with the SwissTopo maps, or the highly regarded (though I do not use them) Kümmerly+Frey Excursion maps (if you get the German page, just click on the English label on the far right).

And yes, the SwissTopo 1:25,000 digital maps, with the Swiss Hiking Federation trails, are an excellent investment. If, like me, you only hike in one of their eight regions they are more or less affordable.