When comparing Rosegarden vs Soundslice, the Slant community recommends Rosegarden for most people. In the question“What is the best free music composing (notation based) software?” Rosegarden is ranked 3rd while Soundslice is ranked 5th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Wonderful MIDI support
Pro Web-based
Nothing to download or install.
Pro Imports Guitar Pro files
Great support for importing Guitar Pro files, of which there are many across the internet.
Pro Imports MusicXML
Great support for importing MusicXML from other notation editors.
Pro Great for transcribing
The editor can sync with YouTube videos or MP3s, which makes for a very efficient transcription workflow.
Pro Free
The basic version is free, though there are paid features such as ability to add custom keyboard shortcuts.
Cons
Con Virtually zero plugin support
No VST, VST2, LV2 or LAPSDA support
Con Very complicated
Con Little control over engraving
The sheet music is "responsive," meaning it wraps to fit whatever device you're on. So this isn't intended for creating notation for print publication — it is native to the web.