I have a small 6" tweezers with the curved-pointy end and that works great for planting hair grass, small stem plants and picking up tiny things. The larger 12" tweezers, I use to get at something at the back of tank for instance, but it's just too thick at the tip to actually use to plant something in gravel. If I had to choose only one I'd go with the smaller 6" with the curved-pointy tip.
30g Juwel Rio Male Guppies, Dwarf Shrimp, Ramshorn snails. (since Mar 07)
14g in storage (Oct 06 - Jul 09)
6g QT (since Jan 09)