At the risk of derailing your thread, I don't use either. There is no real game reason to frequently have dwarfs change professions. The main thing I find is trying to keep track of what the dwarfs actually do -- so that you can debug problems if some job isn't getting done. I have 2 ways in the current game to deal with this at the moment. First I set the custom profession to all the labours that a dwarf is set to. This is a PITA in the early game because some dwarfs will end up with 4 things. But as the game progresses, there isn't much need to have more than 2 labours on each dwarf. Eventually one of them even becomes their normal "profession" (so they get the appropriate colour and are sorted in the "U" screen appropriately).
The second things I've started doing is restricting workshops to specific dwarfs -- each workshop allows only 1 or 2 dwarfs. I then label the workshops after the dwarfs. You can use the "R" command to then browse through the locations to zoom to the workshops (or just "k" over it if you happen to see it). This tells you what dwarf is supposed to work there. What's even nicer is that if you only have one dwarf assigned to a workshop, when you "q" over the workshop, it tells you what the dwarf is currently doing! Since I've started doing this, I've come to the conclusion that this might be Toady's intent on how workshops are supposed to be set up (which is probably why there are like 20 of each kind of workshop in world gen fortresses).
DT provides a lot of other handy information. It also allows you to more easily choose dwarfs that are suited for a particular task. I've never actually used DT myself, but I can see the appeal. The one thing I find, though, is that for most jobs the traits a dwarf needs is pretty insignificant in the grand scheme of things -- even the worst dwarf can train up to legendary status in 2-3 years for some jobs. Even where it is significant (usually you need strength to haul things around efficiently), you can often train up the stats in the military.
I fully admit that when I first started playing DF, I had tons of spreadsheets where I manually kept information (I might as well have been using DT). As I've continued playing, I've searched for in game ways to give me the information I need. I recently started keeping a "shopping list" for foods I want to buy to satisfy dwarf preferences (this would be something that would be a great addition to DT if it's not already there). Otherwise I keep no out of game notes. In a lot of ways it seems to work better than when I was trying to track every detail. YMMV.
I guess one other small thing -- I use the manager for virtually every job in the fortress. I *highly* recommend this approach. It takes time to learn and a lot of experimentation. It also means doing some upfront thinking about your workflows and probably how you have your stockpiles set up. It pays off in spades, though. Once I have my fortress set up, I can just concentrate on solving problems and not have to micromanage the whole thing. More than anything, this is the thing I think people should concentrate on if they don't have experience with it.