I use OSMdroid lib v.3.x in some game, where markers are the main part, represent the gamers and their bases. Tested with qty up to about 100 markers. I have to say that OSM is very "heavy" solution, need lot's of memory, app is slow very often even on modern devices (even with several markers). OutOfMemory error is regular thing, ecpecially on Android 4.0.x.to help me decide whether to go with Osmdroid or GMaps since the subject is totally new to me. Sadly, no response so far.
But no implementing limitations, comparing to Google Maps.
But Google Map v.2 requiring the registration and existing Google Services - works with 500 markers without any speed issues.