It depends on you really. You could totally spend a week in the area riding nothing but waymarked trails and easy to find “secrets”, if you’ve got transport and can get to the other resorts around the area (ps, La Thuile and Pila are absolute musts). St Foy has great riding but even having ridden there a few times I couldn’t find most of it again and I definitely couldn’t understand how the uplift works… So you’ll not run out of riding. I could spend day after day at any of the resorts and still be enjoying it.
But… You could do better, with a guide. You’ll ride the best stuff, you’ll ride stuff you didn’t even know existed, and you’ll largely avoid the crap and even the average. I’ve never had to use the backup but it’s there. And it gives your week a structure and stops you wasting time. Looking at the holiday as a total package, guiding doesn’t add an awful lot but you’ll get a lot back so it’s basically a multiplier, imo.
What I’d really like to do is do a week guided then a week selfpowered, reriding routes while they were fresh, smashing out repeat runs, etc (you’ll very rarely ride the same trail twice with a guide, but sometimes I’d like to- I don’t know how many runs of double header, ace of spades, the bottom of Pila or K2 at La Thuile I could do without getting bored, but it’s a lot.)