Short Answer, use both, long answer read on.
I have 2 NT1 mics but the very early versions that were out before they released the NT1A, I also have an old (early) NT2 and they are great, in fact the NT1 mics I have sound almost the same as the NT2 but they have not omni mode. I also have an NT1000
Now to guitar, I use my NT1 mics all the time on guitar cabs, sometimes I use a NT1 and a SM57 which is my favourite set up, I just blend the 2 together or sometimes pan on left and one right. But I sometimes try other mics, MXL V67G, a senheisser
ME20 Omni, Sennheiser 421, try anything, SM58 and a mix of any of these. The NT1A you have should get a great sound don't worry about other people say.
I position the mice just off the speaker cloth and about 2/3 out from the centre of the speaker, if it's too bassey I move it into the centre slightly or too bright towards the edge, this makes a big difference. Don't put too much bass on the amp as it turns to mud (a common guitar player thing).
Sometimes I set up room mics a meter or 2 from the amp and blend this with a close mic, this only works if we are recording guitar on it's own, the room sounds good (which it does), and it's the sound we actually want.
And yes I use compression when mixing, again all different settings and brands depending on what I want.
Cheers
Alan.
P.S I am in OZ