I hate this sort of debate. there is no one way to play bass-fingers, pick, thumb. It all depends on the style and what sound you want. Flat pick will get you a sharp attack with plenty of highend, great if you are not competing with two or more guitars. At first, playing steady 16th notes will seem easier using up-and-down strokes, but how much rock music requires that? The first priority is to put out BASS, bottom end. With that your main focus, attack becomes secondary.
Here's a couple questions for all of you, how important is compression in getting your sound out? How do you get clicks and clanks (an issue with thinking between pick and finger, fingers can make noise) down to a minimum?
Fingers takes a more disciplined approach, you have to be very consistent how you strike the strings. But there are ways to vary it, angle of attack, force.
Flat picking is just one sound, really, and less flexible. But it's not "wrong" either.
Maybe I'm an old fart, but think Chris Squire (Yes, flat pick) vs. Geddy Lee (Rush, fingers). What's the big difference? And I am a fan of both.