[nst7]

The 003 or mbox 2 should work fine, with no additional latency. Keep in mind each program has it's own way to set buffer sizes (usually under "preferences"), which affect latency. So You might have protools set to 128, then have Reason set to 512 and the latency will be different, not because of the hardware, but because you might have set the settings different in each program (usually it's at whatever it was the last time you used it). You may already know this, but when recording you want low buffer setting (so there's no delay) and when mixing you can use higher settings (easier on processing power).

However, on the 003, the hardware will only work with one application at a time. If protools is open, you won't be able to hear audio through the 003 from any other program (though you'll be able to hear it on your computer speakers). If you close protools, you can use it with your other programs. I've heard this might be different on the mboxes, but I'm not sure.