I think we're all kinda getting mixed up on what the OP is asking. Unless he really is dumb and is asking what's bigger, the number 3 with decimals or infinite, that's not what it seems like he's asking.
He's asking whats bigger, infinite or how long pi goes on for. If pi goes on infinitively, then they'd be the same. If it doesn't, infinite is bigger because pi would stop
either way the questions kinda dumb it seems as it's just "does pi go on for infinity"
that's the only logical question unless, like i said, he really is asking "WHATS BIGGER 3 OR INFINITE HURP"