Should I use Mod Rewrite to change these URLS?

I am putting a commerce site together and the cart software I'm using (cubecart 4.x) has a "use search Friendly URLS" option. Is it worth the effort to change these urls? Or should I just leave this alone?

The category urls look like: www.mystore.com/corsets/cat19.html. Would this be a better url as: www.mystore.com/lingerie/corsets/ ?

The product pages look like: www.mystore.com/push-up-corset/prod_46.html. Would this be better as: www.mystore.com/lingerie/corsets/push-up-corset/ ?

How much difference over the long haul in serps will rewriting these make? I'm new to mod rewrite. Am I setting myself up for needing a new rewrite rule *every single* time I add a product to the site?

Thanks!