The choice becomes clearer when looking at upgrading the deck, though: Marneus wins for me, hands down
Creatures you control can attack as though they didnt have defender, is the next line of text on Felothar, referring to an ability thats so central to the games core design that it was retroactively added to cards dating back to Magics first set, Alpha
If you do, return the chosen card to the battlefield
That said, even just one or two would make one-of sideboard cards go a bit further
First, we're going to take a look at the blue and white (Azorius) Buckle Up deck, which revolves around pilots and vehicles, using the Commander Kotori, Pilot Prodigy to make every vehicle (including a very nice included Parhelion II) easy to crew and effective in combat
Once again, whether youre playing Commander, Pioneer, Modern, Standard, or Legacy, youll often be running into this powerhouse land