I had a Kat/SR back in the day and now I have a Kat/WP scrapper. I definitely like the WP more than the SR.
In some instances you can never have too much defense (higher level mobs, def debuffs) and also consider that DA's def boost is very specific (melee and lethal only) so it's nice but not OMG. I use it as part of attack chain just to keep that edge up.
I find WP to be a great set and forget secondary and I like the mix of tools (regen, def and res). I've also played regen, dark and inv secondaries as well and WP is by far my favorite.