[case3]

Even for the most mathematically oriented player using a baseline percentage increase in hand value will lead to incorrectly valuing hand strength preflop.

Looking at the example above the suited hand wins about 3% more often overall, relative to its off suit rate though it improves 15%. Put another way imagine if a hand won 1% of the time, an increase to 2% would only be 1% more but it would be winning twice as often.

More importantly a suited hand can make a flush or flush draw more often than an off suit hand and that value is what make the difference.

Two examples:

AK vs a random hand in a 2 person HU game. The suited AK would win a showdown about 1.7% more often from an already high 65%, aside from that the majority of hands would be played with the value of AK making a pair or showing down unimproved.

23 vs a 8 way field of probable holdings. The suited hand would, in a showdown situation, win about 3% more, or 30% relative. Playing the hand with out assuming a showdown the suited hand is a great improvement. In a hand like this 32 needs to make a flush, wheel, or maybe 2pair/trips to win. The flush is a big part of these strong made hands needed to win.