it all depends how and where u gonna use your navi..
i can see that you put 'good price' as the first priority on the list, so meaning u wont b willing to spend more than $400.. *i guess
if u r in city, tall buildings all around, portable ones are most likely very inaccurate.. hard to get signal/all the 8(or 6) satellites.. so, u probably better off start looking at road signs ><"
portables ones are not tat useful/good when u r tooo far out into country side as well, which is in my case, i am always looking at rural lands..
even if u spend top dollar($1k-2.5k) for blaupunkt, pioneer, eclipse, kenwood....(HU tat read map from CD, not memory card-sd card) with the function that they can calculate where u r even with minimal signal, as it is reading your ACTUAL on-road speed (not the speed reading thru satellites), u still hv problem like.. cant upload the speed and red light camera into the POI (which many ppl will find tat very useful..) Not that the disc which cost $2xx-3xx to update, doesnt include the POI for speed and red light, is tat the HU itself is not design/program to show those POIs..
tat's why i have 4 different navigators on 2 cars, including 2 portable and 2 built in. (and map on each car, overkill?? )
but if u just using it like normal ppl do, u like spending as little as u can, downloading updating maps online for free, and get free POI for updated speed/red light cam (or mayb just little cost, go ebay~), then portable is your way, dont worry too much on brands.. same thing
it is still always good, to keep a map in your car, which i find it very useful..
p/s: in dash ones are really good, but prepare to spend a lot if u wanna update it.. which is only once in 1-3 years??
experience: owned 4 different portable ones(kept 2), and 2 in-dash