The 19" will probably be too big unless you have gorilla arms... Gary has a reputation for very long top tubes w/ a mid length stem. What you need to do is figure out your current bike's cockpit size (or get sized properly) and then look to see what size has a similar setup. If you look up Fisher's website you can get very detailed geometry and measurements off of there.

It sounds to me like you should be on a 17.5" if you are 5'10-ish since reach is far more important than inseam (they make longer seatposts, but you can't add/subtract top tube).

The idea behind compact geometry (sloping top tube) is that you only have to worry about reach and not standover (to an extent) resulting in a better fit... so if you have a good reach on the 17.5 but a lot of standover, the standover clearance should not sway your decision.