May I suggest?
"they tell you WHAT features a given unit has but not WHY you want/need that feature."
See if there's a US Power Squadrons group in your area, sign up for the navigation class. Or, download a copy of Bowditch (or buy one, any recent edition) and read the navigation sections.
Getting a bigger picture of what and how you may need to navigate will probably help you to make sense of the new toys and their features.
Make haste slowly, the price on this stuff simply comes down every year.