Funny Lingus explained :
The free sites are just an advertising gateway to paid sites and offer
nothing of substance.

Sorry, I cannot agree apart from the the past about a certain free site
trying to entice you onto a paid site. I admit to have never researched
the paid sites, but a certain free site is rather good, quite genuine.
As you would expect - you do need to use great care and be wary of some
of the motives for being there.