Fillets give better flow (less resistance) than chamfers. Fillets will never give a UL/NSF or whatever regulatory inspector a reason to ding you for a sharp edge or burr (unless a machinist really bungles it). Fillets give generally lower stress concentration factors.
Chamfers generally are more forgiving when fitting mating parts.
On a finish turn I would always put a .010 fillet on every corner because when turning any angular turn the tool tip will leave the finished surface and could cause a sharp edge. The extra time is undetectable but the lack of sharp edges will be a joy to your customer and you.
If you are making the cut based on the shape of tool, and you have various sizes of 'edge break' on the piece then chamfering is better. For each rad you need a tool change where as within reason one tool can create chamfers of varying sizes.
General consensus around my place is that chamfer is a bit cheaper.
Of course, senior management, industrial designers etc ten to prefer fillets.
I read somewhere, may be on this forum, that protective coating (like paint) may have some issues with chamfers. Thickness of coating is reduced on sharp corners of chamfer so coating is lost on those places first or something similar.
I don't have first hand experience, just reiterating something I read.
It really depends on how the part is being produced.
Sometimes chamfers are easier to produce other times rads are. For example a milled pocket with chamfers is a real no no.
The same applies to wire erosion, laser cutting, water jet etc you will always get a rad so with a chamfer you still get two rads on that chamfer on internal corners.
Technically, fillets, whether round or angular, are generally referred to as such at an inside corner, while chamfers or radii are the term for an outside feature.
For outside corners, a chamfer is sometimes regarded as a straight line with a burr at each end. Unless the blueprint gets in the way, I always program a tiny blend radius at each end of a chamfer, for the ultimate in a beautiful, functional part.
