we did play 3-5-2 previously (under roy evans). Yes, this formation will make your midfield compact (so opposition will find it tuff to penetrate your half).
But the main problem of this formation is that there will lack of width. You only have 1 man in each flank. Thus, most of our attack was through the centre (which the opposition easily contained).
There are lot of pros and cons of using 3-5-2.....we should use it depending on the situation or opposition (eg...2nd half against Milan in euro champ final

Still prefer 4-4-2 though. With wingers and fullbacks down the wings, a lot of chances will be created.