I can't find any reviews on the Navi and am leaning towards the Emcast. Any info on either would be appreciated.

I've just bought two navi xta's with the baitrunner spool and sold my emcasts. Nothing wrong with the emcasts, for the money they're really good. I just wanted a quicker transition from freespool to drag and the xta does the job.
The Navi is just as smooth as the emcasts (has less ball bearings though) and is a similar weight; the spare spool(2 spare with xsa,1 with xta) on the navi is graphite, alloy with the emcast. Both have good winching power,both have a good drag, both are annoyingly too "free" and the handle spins round when trying to set up bobbins when legering!
If you can, go and have a play with both- i suspect it'll come down to which colour you prefer! ;-)
P.S. The xta's are only £60 if you shop about.

Thanks Paul - it's the quick transition that might make the difference for me too, having used regular baitrunners in the past.

i bought 3 navi xta,s 2 months ago all i can say is for the price i cant find a problem with them great line lay awesome casting ability and good and strong being a shimano u no your getting a good trust worthy reel like paul said if you look around you can get them for 60 quid (happy days)

Thanks guys - I'm going to have a look at both next week. Decisions, Decisions...!