[need-for-accord]

if you don't care about the hanging cables mess and windshield mounts dropping from the windshield while you drive take the regular model and use a portable GPS.
If you prefer a neat and clean dash and windshield get the indash nav model. Be aware that its more expensive and that in a couple of years the in dash system will not be top notch and you will not be able to upgrade it.

Besides, in dash GPS voice control is so cool! You can ask things like: What time is it, Air conditioner On, Go Home (gets you directions to go in saved address), radio on, etc..