This is only a personal opinion but I feel that there are so many Properties out there for rental (mine included) that that market is alittle saturated.
I looked at using holiday rental websites to advertise on but when I first looked at http://www.holidaylettings.co.uk
they only had 3 properties in Bansko, they now have 61 and expect this to rise.
I have nothing against the above mentioned website, nor others that are like it but I think trying to get your own rentals is a better option and more cost effective.
Good luck with whatever you choose !