Hey! I've owned both. Do you want a compressor "effect" or do you want a compressor for practical reasons - ie; string leveling, peak limiting, light smoothing, etc.
The pigtronix is fantastic at making you sound like you're playing through a compressor, and it's a great sound.
The Aguilar is quite transparent; there's a slight sharpening of the highs, and tightening of the lows, but not much more.
The pigtronix has the added bonus of the grit switch, which gives you a pretty cool distortion sound, I've never found anything quite like it.
The Aguilar is still on my board, the pigtronix is gone. I run the Aggie after my filter and as a peak limiter on bass, I run it when I finger pick on guitar; it's great at both. I've run in always on before; it's good at that, but I've outgrown the need for that - now I just get natural compression from my tube head.