I was looking at two specific brands ( TomTom and Garmin). I found the Garmin Nuvi 650 for $339 and the TomTom One XL is like $350. Which would you guys prefer? Any better options or prices avaliable throw them at me. Thanks!

Go with Garmin.  They've been around longer, and offer more options in the way of maps, etc ...

Now what would be nice would be if you could take the chip out of the Garmin, put in the lake chip and be able to put the unit in your boat too

Have a Garmin's in the FJ Cruiser and a TomTom in the Duramax. Both are great and do the trick. Wouldnt take one over the other, same thing imo.

I know Lowrance has an Automobile and Boat GPS in one but I dont think either one would be great. I think it would provide minimal for both. Are there any combo's out there that are good for boat and autos?

My I-finder H2O works great on the lake with the navionics chip and in the car with the Map Create chip.  The only problem is that the screen is too small for my ageing eyes.

I really like the Lowrance iWay® 600C, but it is way above my price range.