isailor gets good reviews
... I have installed it, but not figured it out yet.
also decent (but no night mode with red backlight like isailor has). Navionics
have a bit of a rep for refusing to update older versions and making you pay for a newer version... not very friendly...
These are the two that I have.
I don't have a stand alone gps
(save for the display on my vhf) so can't comment.
is mounted in a lifeproof nuud case and attached to pedestal
via a ram mount. Works fine (bimini provides shade to make screen
readable even in direct sun).