OK I am putting my neck on the line here with a posting about tyres but be gentle with me please 😀 techincally this is not a "which tyre thread" because i already decided on some Medusas. but dont know what size to get 1.8 or 2.1 ? Its for a 100mm hardtail for muddy marathons, I am a relative lightweight 65kgs.
Was originally thinking 1.8 on the back and a 2.1 up front, but before I decide would like some previous users advice on the other options as follows:-
Would 2.1's at both ends not be enough of an advantage in the mud as a skinnier mud tyre.

or

Would a 1.8 at both ends be far too condition specific for a marathon where even on the worst weather days things can dry out and surfaces vary ?