crystals from one maltsters to another's flavor profile changes, subtle, but noticeable.
when you see 35L 45L etc., they are euro/German malting's, Americans go by tens evenly.
malts like Maris Otter pale malt from Baird's and Maris Otter pale malt from Fawcett are different flavor profiles although they are the same cultivar and malted as pale malt.
maltsters products differ in flavor profiles, so once you find the one you like, stick with the same malts.
you'll see recipes that call for a certain brand name of malt. when you come across one of those, if possible, use that brand malt, because the outcome Will be different using another brands malt substitute