They are the same dovetail jig. The only difference is the 4212 has another template for through dovetails that the 4210 doesn't have. The 4212 should have templates for through dovetails, box joints, half-blind dovetails & more. I would get the 4212 since it has an added template that you would not have to buy later. The 4210 has a template for half-blind, rabbeted half-blind and sliding dovetails. Same price or close get the 4212.
Have a nice & safe day!
Last edited by jlord; 06-27-2011 at 07:04 PM.