[Zubersoft]

I'm probably not the right person to answer your questions, as you could say I have a bias being the creator of MobileSheets, but I will say that there aren't that many functional differences between forScore and MobileSheets as far as what you can do and what features are supported. Each app takes a different approach to some things like file storage and management, the relationship between songs/pieces and files, supported metadata, and the organization and presentation of the user library, but you can still accomplish all of the same goals with each app. 

• If you use MIDI, both apps support that. 
  
• If you need buttons that can be pressed to trigger actions, or link points to jump between pages, both apps support that. 
  
• If you need to reorder, duplicate, or remove pages, both apps support that. 
  
• If you need to annotate, add custom stamps, use layers, etc, both apps support that. 
  
• Both apps support a single page display, half page display with adjustable half page turn positions and a two page mode. MobileSheets also supports a vertical scrolling display mode though, and supports automatic scrolling, which forScore does not support. 
  
• forScore supports face gestures with a pro subscription, but that's something I'm adding in the next major update for all users free of charge. 
  
• Both apps support extensive sharing features where you can export proprietary file types (i.e. 4sc vs msf) that can be imported on another device. 
  
• MobileSheets has a free companion you can run on your PC, but you can also just run MobileSheets on a PC and forScore on a Mac. 
  
• MobileSheets supports text and chord pro files which forScore does not support. 
  
• Both apps support importing index files for PDFs to pick individual songs to add. 
  
• MobileSheets allows many songs to all utilize the same PDF to conserve storage space which is not something forScore allows (to my knowledge), which is useful with Fakebooks and Realbooks. 
  
• I'm fairly biased, but I like the library management and organization better in MobileSheets (but that's not surprising as I originally designed it for myself), as MobileSheets has a dedicated library screen for finding songs, setlists, collections, etc, while forScore does everything through one central screen with popups. 
  
• Both apps support playing back audio, adjusting the playback speed and pitch, and both apps support adding notes for songs (I believe). 
  
• Both apps support library synchronization as well as library backup/restore, but forScore has an automatic cloud sync using iCloud, whereas MobileSheets requires the sync to be triggered manually (although an automatic sync will be added next year). 
  
• MobileSheets obviously supports the three major platforms while forScore is iOS/iPadOS/MacOS only. forScore has a slicker UI with a more cohesive theme and looks at home on iOS, whereas MobileSheets has a somewhat dated appearance as it has been updated piecemeal over the years and doesn't fully embrace the material design from Android (this is another thing I hope to eventually address). 
  
• Both apps support a built-in metronome, although forScore's metronome UI looks nicer, while the metronome is playing, there is an LED counter in MobileSheets that works quite well. 
  

One last thing I should mention is that MobileSheets supports multiple files per song (and you can use image files), while forScore only has one PDF per song to my knowledge. I have a bunch of really nice PDF features coming in the next update as well as image correction features to make it on par with what forScore offers. MobileSheets uses a third party library for capturing and correcting images, and this makes taking pictures much more feasible (I've gotten a lot of positive feedback about this). 

I think I covered most things there, although I'm sure there are things I'm forgetting. If you have specific questions about features you need, let me know and I can answer them.

Mike

UPDATE:

• One thing I didn't mention is that forScore allows pages to be turned at specific positions when playing audio tracks. MobileSheets doesn't currently support that (it's on my list of things to do). 
  
• forScore also has an iPhone version, but the iPhone version of MobileSheets is being rolled out very soon.
  
• forScore supports Stage Manager a little better, as you can have multiple forScore instances up essentially, allowing you to load multiple different scores at once. 
  
• forScore also supports tabs while MobileSheets does not.
  
• forScore supports Apple Music for audio, while MobileSheets only supports audio files on the device. 
  
• Both apps support creating multiple libraries and switching between them. 
  
• forScore supports bookmarks that can be added to setlists, whereas MobileSheets uses a "Create Snippet" feature which adds a new song to the library that shares the same file as the original song but uses a different page range. 
  
• forScore supports tracking metrics, but this hasn't been added yet to MobileSheets.
  
• forScore supports a virtual piano keyboard to play notes on, but MobileSheets does not yet have that.
  
• forScore supports recording audio. 
  

Whether these matter to you depends on what features you are currently utilizing.