I have 2 chainsaws and I prefer to hand file my chains between occasional professional sharpenings to reset the chains and fix any accumulated error caused from hand sharpening. For me, it is not usually necessary to get the professional sharpening because I am very careful and conscientious with the file when sharpening, but I do it anyways. Dremels and other abrasive sharpeners can very easily overheat the blade edges and cause a loss of blade temper if you don't know what you are doing and go very slowly. That softening of the blade edges would cause your blade to dull very fast from then on and you would need to sharpen it constantly to keep a good cutting efficiency. There is nothing you can easily do to reverse that once it happens as well, your chain is basically just junk. You don't have to worry about that if you hand file your chain.
I have a nice Stihl 031av as my main firewood chainsaw, but I use and really like a product that Husqvarna makes for sharpening my chains. It is just a small stamped metal piece that has rollers on each side. It fits right over your chain while it is still on the bar and it holds your round file at the correct angle and also holds it horizontal to the blade as well for a very simple and cheap way to get good sharp blades.
If I remember correctly it only cost something like $15-20 and it came with a set of files as well. There is also a small flip out depth gauge for accurately and quickly setting your rakers at the correct height, and the gauge has two settings, one for softwood cutting, and one for hardwood cutting. The thing as a whole is very simple, small, easy to carry, and easy to use in my opinion. There are some videos on YouTube etc of people using it. I bought mine from Amazon about 2 years ago or so and it has never given me any problems.
The file-n-joint tool linked to and mentioned previously in this thread is in fact a great tool (I don't have that brand, but I do have a similar style sharpener), but to me it is more for sharpening a chainsaw blade on a workbench inside a shop etc. The tool I mention is a little bit less accurate overall, but it is still more than accurate enough to sharpen a chain quickly and easily to a high standard and great for sharpening and keeping your blade sharp while in the woods cutting trees, because it fits in your pocket very easily and requires almost no setup etc, so it depends on your application which one would work better for you.