Unfortunately the answer to that leads to a religious debate. If you love the classics and are looking to recreate the sound and feel of the originals then a 4 way would be your best bet. But if you would trade that for real estate on the CP and usefulness in other games, then a 49 way might be for you.
I have a buddy with 2 49 ways and no dedicated 4 way. Playing 4 way games on his machine is fine with me. It doesn't feel or sound the same, but I am looking to have fun, not recreate the originals.
I have 2 8 ways and a dedicated 4 way. I usually end up playing the 4 way games with the 4 way stick.
If you love the old games that much you might consider finding a way to put a 4 way on your board. I have never seen a control panel that doesn't have room for a 4 way stick, but yours may be different. And I don't know what else you have planned for the board so it is hard to say.