Many of us have used a "cheaper" wetsuit for diving than
some "dive" brand.   They typically don't have zippered
ankles or knee pads, etc. like dive suits do.
It's all in what you get and pay for.

I've found they don't hold up as well.

Of course now days their are also 'el-cheapo' dive suits
also.   So you can still get cheaper stuff.

Overall get what works for you and for what type
diving you do.  If a surfing suit works for you
instead of some more expensive "dive brand", then
use it.