I'd have trouble characterizing Collings relative to a Martin. I mean, Collings are built on a Martin model (well, except for the ones built on a Gibson model). I suppose of the dozens of Collings I've played I would only conclude...

1. On the whole the Collings seem to use better wood. They should -- they're no bargain guitar.

2. Martins are no slouch in the finish department, but Collings are flawless. They also include some VERY cool customs (like shaded tops and sunbursts that rival any being done today.

3. They seem across the board to be stronger "fundamentally" -- that is, they may resonate and sustain like many contemporary guitars, but not at the sacrifice of havinig to suffer lots of harmonics flying around.

4. Collings mandolins are out-of-the-factory stunning in sound.

I suppose the difference you summed up (what you sensed) between yours and the Collings maybe falls into my point #3. Some seem to feel that that really prominent bass isn't always a good thing -- and it often seems to confuse or mask over intricacies of sound that you might really want in there.

I like Collings, but then, I like guitars.