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Here's the link of the Carolina Marshmallow mats you are talking about:
http://www.gymnasticsstuff.com/GymnasticsMats.htm
And here's the pricing:
http://www.gymnasticsstuff.com/DismountMats.htm
"Marshmallow Mats are really a whole system of landing and drills mats. Use them as a tumbling strip, for drills, or stacked as a level 4 vault system! You can create a pit area to finish skills for bars, beam, floor, vault or at the end of your tumble tramp!"
I haven't used them, but it would seem like tumble track would be bouncier and get you up higher to practice the skills, as it is like a long trampoline - the tight ones (the black trampoline part) are good, not flimsy or loose, or saggy.