Go to Navonics web site and check out what lakes are covered on the mapping card for your area and how many of those are of lakes that you plan on fishing.
The HD maps are the ones that have the good survey/scan information. If the map card HD maps covers water you frequent a lot then the card is of more value to you, if the lakes you fish are not covered then of course not as good in your application. Where I live the HD maps only cover lakes I normally will not be fishing so the map cards have little value to me.
But the mapping feature along with a zero lines card allows me to map lakes and smaller rivers that I normally fish that have no mapping at all and to me this is where the value is in HB mapping capability.
Even if you do not get the navonics card get a Zero line mapping card to make your own maps with contour lines while you are fishing.