Definitely get polarised lenses, but be aware that polarisation quality can vary. I got some prescription polarised lens for my Ray Bans from an online supplier, and the quality of the polarisation was very disappointing.
You can test polarisation by holding the glasses up to an LCD laptop screen or monitor. When held horizontally the glasses should be quite transparent and when held vertically they should be totally opaque.
You can see in the images below that my replacement lenses were blotchy in both orientations when compared to the genuine Ray Ban polarised lenses.
I've also heard similar things about some cheap Chinese polarised sunglasses, so check before you buy.