Having taught myself and 2 kids with sen (including dyslexia, dyspraxia, learning difficulties, SPD) to type and used MB, Nessy fingers and EnglishType Junior...
would say ETJnr is by far the best... not the most exciting but in terms of progression and logical typing being taught - it starts with the home row, then the top, then the bottom then shift keys. Nothing onscreen moving about to distract...
Nessy - games by far more exciting - but in sensory terms too many noises, bings and pings to distract and the way it teaches the keys although logical in alphabetical order, is harder to master as lots of 'stretches' from the start where as with ET - they are all 'under the fingers' to start with.
MB I found frustrating as crashed a lot and especially once into shift keys was using an american keyboard placement and also the american spellings not helpful from a dyslexia point of view.
BBC type mat is similar in progression to et junior (free on BBC website) but drove me crazy and very slow as every time you play you have to go through some pretty inane animations!!!
hope that helps - has really helped my dyspraxic / dyslexic child who is a fully time typer now in high school rather than writing!