Also, the gray vs. black fuel lines are for different applications ...
A1 - Fuel feed hose; Black in color, has a fire resistant cover; designed to have fuel in the hose at all times, made for use below decks or under engine hatches, say on inboard or I/O motors ... it has the highest fire resistance.
B2 - Fuel feed hose; Gray in color without a fire resistant cover; designed to have fuel in the hose at all times; intended for non-enclosed spaces, read 'above deck' or open air use.
Both allegedly are made to the same SAE J1527 marine standard for use with alcohol fuels, however the construction on the tube/liner is different, where it is spiral/laminated on the heavier A1 hose. Yes it is a premium hose and yes, you will pay for it.
But I will tell you that I myself would NEVER use the cheaper gray B hose on any large HP fuel injected motor, 2 or 4-stroke. The lining on the gray B hoses has been known to break down internally and cause problems, have seen it myself - the inside lining delaminates from the outside gray housing and the lining gets sucked flat inside.
I have yet to see any A1 hose breakdown that was less than 25-years+ of age/use ...