It's difficult to direct a response against the question, because it depends on a number of factors including your build, the time (e.g. midgame/lategame), etc.
However I can comment on the muta/ling/bane strategy you mentioned. In those types of builds Zerg players drive back medivacs with a combination of spores, speed zerglings, banelings and mutas. Ideally a combination of those units are used instead of a single unit e.g. only lings. The reason for this is because a good drop is usually placed in a mineral line or a corner giving very little surface area making lings very cost inefficient. However a combination of lings + banes is effective because they can't kite, meaning they can only lift, and that's where the mutas come to punish the lift.
Though mutas are cost inefficient vs marines, a good clump of mutas can still handle a small group of marines. Often it is better to lose a few mutas vs losing a base, again I'm giving very general advise. Another advantage that mutas have against medivacs is that they're fast, as such they are good at intercepting drops before they occur or as they are leaving your base.
Lastly the greatest defense against drops in my opinion is scouting. Properly positioned overlords and good creep spread will tell you a drop is coming giving you ample time to position your units to either counter attack or defend.
Against this is more of an advice rather than answer, but this is way too long for a comment :P