DWV fittings: when to use a sweep instead of an elbow
If you are going by the International Residential Code, you are limited on what types of fittings you can use for sanitary drainage (see table 706.3 from the 2015 IRC below), but there are no restrictions on the fittings that can be used for venting as long as you maintain sufficient slope. Similar restrictions likely exist in the Universal Plumbing Code, but I am not as familiar.

The reason that certain fittings are restricted is to allow sufficient transition to help prevent solid waste from clogging in the drain (note that some of the restrictions are lifted for 2" and smaller pipe sizes because these pipes cannot carry any sizeable solids).