Either one will work.

New injectors will be essentially plug-n-play and you know they're in good shape. They're also like $80 a pop.

Used DSMs will require you to scour the junkyards for some additionall parts and you'll have to put some more time into installing them. You might also want to send them to RC to have them cleaned and flow balanced. But it'll be cheaper.

The decision is up to you man. If you can slang the extra coin I'd go for a set of new RCs personally.