Is the bc337 and 2n4401 similar enough to use each other?

For many applications, yes. 
The BC337 comes in different gain grades, but the 2N4401 is about in the middle of the middle grade. The 4401 is a bit faster, but has a bit lower voltage and lower max current rating. But if you operate it with under 40 volts collector to emitter and with a collector current no higher than 100 mA, they should both work well in most circuits. 
Note that you have to reverse the flat side orientation to get the leads to have the same definitions.