Allen...
Good advice already. The long way. Too many wood movement concerns the other way as Chris says. Long way looks better, too, as everybody says.
I can tell you what I would do to achieve a 60x20 top glued up from 1x4's. Get six 1x4s 6ft long. What would be even better is to get them rough-sawn (4-quarter) and surface them yourself, because surfaced 1-by is about 3/4" thick and I'll give you 20-to-1 you won't get them glued up so evenly that you won't have to take some off to get it flat. So you'll end up with a top that's less than 3/4. Which is probably okay with a credenza because you can provide enough internal support. Just saying. Why 1x4s?
Long grain glue joints (ie, side-by-side) are very strong, as Jim says. If you bang a long grain glue joint apart it probably won't break at the glue line. Biscuits in this case are to help alignment, not strength.
Also as Jim says, pay attention to grain direction. Two things about grain here...when you get your boards lay them out side-by-side and decide which direction they should be milled (ie, find the "uphill" direction on each board). Keep them aligned in this direction...if you don't, when you plane them after glue-up you'll wonder why some are tearing out and others aren't. After deciding that, choose the juxtapositions that afford the most pleasing affect...then mark them. You can move them around and turn them over, but don't flip them end for end.
Will you be using a jointer to prepare the edges?...if so, keep in mind that no matter how careful you are it's not likely that you'll get the fence exactly perpendicular to the table (you'll put your Starrett square against it and think it is, but it won't be). If you joint each board such that the error accumulates you'll find that you can't slide them together and have them cozy up without a gap...then when you try to pull them together with clamps you'll have a built-in cup. The solution (well, one solution, works for me) is to figure out for any two mating boards which side goes against the fence and which direction through the jointer so that when they are side-by-side the error cancels. This will require you to joint some boards in the "wrong" direction, so keep the final pass light to minimize tearout (on the other hand the tearout is inside the joint so it doesn't matter).
There are various ways to do this kind of a glue-up. Long ago I sprung for the Plano vertical glue press after trying many different kinds of clamps, and if you wanted mine you would have to come armed...anyway, I can't offer much here. Larry has some good suggestions. Lots of stuff on the internet about spacers to keep the boards off the glue table, alternating clamps, cauls, etc. If you do the jointer thing and use biscuits for alignment it will minimize the heart palpitations. There is no glue-up like this that is not accompanied by heart palpitations. Something I saw recently..."I don't wanna be a cabinetmaker no more...the chest pains are now five minutes apart". Consider the glue you will use, and pick one you like with a long open time. I've long used Gorilla glue mainly because of the 15-minute open time, but it does do the polyurethane ooze. On a flat surface this isn't so bad since a scraper makes quick work of cleanup (after curing). The pieces can creep on you, so watch them for about 20 minutes. Recently I've tried Titebond III and so far no complaints...less mess. I think they may be stretching their open time claim a bit though.
Good luck. Would like to know how it turned out.
Cheers.