Garmin nav vs iGO8 & winCE all confusing to me

After a recomendation from Doug T some time back I purchased a nuvi 760...very happy and always found it accuarte and sensible in route planning.

When we purchased the LC 2 years ago I wanted an indash unit that did it all, GPS city navigation, Oziexplorer, radio, CD, ipod etc.

Was recomended the Kenwood DDX7034BT..told not to grt the one with the GPS option because the city nav (garmin?) was not compatible with Oziexplorer. So I was sold a seperate GPS system that displayed on the Kenwood

This is a HiTV . My issue is that all works fine as intended but the city navigator is iGO8 that when compared to my Garmin is very second rate...

amongst the issues when compared to the Garmin are ETA is out by about 50% at the start of a journey..and only correct when you are 5 mins away as it adjusts!....The garmin has always been incredibly accurate ETA regardless of distance of that journey.other examples have been incredibily stupid navigation suggestions in the city and country that being a local i just laughed and ignored....

put the Garmin on the windscreen and ask them both to plan the same journey and they seldom agree (and yes they have the same route instructions, shortest, quickest etc).the Garmin always makes sense

I hate igo8 (probably would not have known any better had I not had the Garmin )

So the dealer informs me I cant have the Garmin on the SD card because of compatibilty issues with either Ozixplorer or winCe (I am not sure which)

I am out of my depth here....can someone please explain what is compatible and what is not

thanks