I have been using a Dremmel to slot mine, but I did try my center punch on a used carto. IMHO, you are better off with the rotary tool. Admittedly, I have had mine forever, but I don't see how a new one would be any better. The bit is a new one, but it could be my problem; so far, the thing has worked on most surfaces. A center punch is not designed to punch a hole but to score a starting point for drilling.
Here are the problems:
1) You really need to secure the carto with a decent set of pliers, preferably a vise grip and place everything on a solid surface.
2) It takes a fair amount of strength to get the center punch to fire. It has a spring inside.
3) It's easy to slip off the cylindrical surface. A center punch works by pressing down on it to load the spring until it hits a trigger.
4) It took several attempts to get a hole punched through. The center punch sends quite a shock through the part, and I am afraid that the shock could easily break apart the solder connection to the Kantal/Nichrome heating element.
5) The impact of the center punch risks distorting the cylinder of the carto which will cause the Liquinator to leak.
Rather than spending $16 on a center punch, you could probably get a far more useful rotary tool for $19 from Harbor freight. It is complete with a whole bunch of accessories. They are always running specials, and you can get a discount coupon for 20% by signing up for the newsletter.
If you buy a rotary tool, please use safety glasses when using a cutoff wheel. Cutoff wheels can shatter so you do need to protect your eyes. Practice cutting slots into a dead carto first.
Won't a hole punch work better on a sheet as opposed to a hollow clynder which is what a carto is? If you deform the clyndrical shape from the pressure of the hole punch, you will have leakage with the Liquinator.
Rotary Tool Kit - 80 Piece Set