Hi legend, I did this last year for the first time so i'm no expert ( but knew before I finished that it was a great event and I'd be back). I just wore normal road running shoes, and never for a second during the run did I think this was a bad choice. My recollection is that it's primarily road, I seem to recall a stretch of very good surface trai from the bottom of pen y pass towards beddgelert, and then much rougher off road on the final decent down to llanberis - memory is a bit vague seem to think maybe it was stoney / rocky it wasn't that long a stretch ( although it felt like it at the time). I'd guess it was 90+ % road so wouldn't consider trail shoes.... Unless maybe it was snowing
Thx for the advice, was a bit surprised at the price for hotels, and decided the hostel looks a good option, im a bit cautious about City centre hostels as sometimes can be a bit noisy, but I'm expecting boston will probably be full of marathon runners so should have a great atmosphere!