The difference between them are:
Hoover FH50230 vs FH50220
images from manufacturer

SpinScrub:
The FH50230 equips with SpinScrub 77 while the FH50220 feature SpinScrub 60.
The SpinScrub 77 has 2 rows of SpinSrcub Brushes (11 Brush Antimicrobial) for cleaning carpets and rugs, the SpinScrub 60 has 1 row of brushes (6 Brush Antimicrobial) with 60 counter-rotating bristles.

Tools:
The FH50230 comes with a SpinScrub Hand Tool for cleaning furniture, stairs, etc. and Squeegee Tool for hard surface floors while the FH50220 does not include.

From the product images, we can find that there are 2 more things:
Spill Pick Up Mode:
The FH50230 has a suction only mode that allows it to run without brush agitation action, this mode is for spill pick-up, while the FH50220 has no option to turn off brushroll.

Edge Cleaners:
The FH50220 has no edge cleaners while the FH50230 features Edge Cleaning Bristles to loosen dirt near baseboards.

Download manuals to learn more:
FH50220 manual: http://hoover.com/file/600/
FH50230 manual: http://hoover.com/file/646/

If you know more difference between Hoover FH50220 and FH50230, please share here.