Is it better to use a serrated knife, or a regular chef's knife that is really sharp?
A really well-sharpened santoku-style chef's knife is usually my choice. But, it does depend on the type of slicing... such as thick/thin discs, wedges, or dicing.
While I understand that a serrated blade can help with slicing a super-ripe tomato, when I want really thin disc-shaped slices, something very sharp and preferably a thinner spine. The favorite in my kitchen is definitely a Henckel santoku chef blade. Some versions can have a very thick spine, and wouldn't work as well, though. This type of choice is also more utilitarian if you're cutting any other veggies at the same time, or making additional cuts in the tomatoes, such as when you're also going to be halving the discs or full-on dicing.
Things I like the thinnest slices on are a ham and cheese melt, roast beef sammy, a sub for the road, and sometimes for a garnish. (hors d'œuvre, anyone?)
Also, when I'm cutting tomatoes into wedges, I also like to use this same type of sharp, non-serrated blade. Otherwise, I find it harder than necessary to do the smaller divisions after the 1/4-of-a-tomato size. I nearly always do 1/8 or 1/12 sized wedges for salad, so it isn't terribly often I use a "real" tomato knife. When I do, is when it's for a lunch and I don't want to sully a larger blade, or when doing large batches. Getting the core out is certainly easiest with a smaller, serrated blade.
I aways use a aerated knife as it doesn't matter how soft the tomato is, it will still slice it with ease
The best tomato knife I ever had, had a high carbon steel blade about 13cm long, and only 1cm in height. The short height and the rough carbon steel surface meant that the slices didn't stick to the blade as you cut, and fell away cleanly. It broke one day when pushed to hard into soft wood chopping block. Never found another one like it
Coated knives like this should be good
Anything this guy sells: http://knifewear.com/
He brings in a bag of ripe tomatoes every morning to show off his blades (and lets customers try them all). The quality of the Japanese steel makes my professional Henkels blades look like toys. He gets all of his blades direct from the masters in Japan. The blades are so sharp, they sort of just fall through the tomatoes...
I use one of these: http://knifewear.com/knife-family.asp?family=5 for most things and have another smaller paring knife to use as well.
But the point is if you use a very sharp knife, you don't need a "tomato" or serrated knife. If your sharp knife doesn't cut through the tomato, it's not sharp.
Disclaimer: I have no affiliation with Knifewear. I just made the mistake of going in one day and buying some knives from him. He has shown me the error of my ways.