Actually, most DCC manufacturers are abandoning the analog feature in the DCC control system, due to non-interest. 10 years ago this was a big deal, but nowadays, most people do not care, as evidenced by the abandoning by most manufacturers. This feature allows someone to run one non-DCC loco on your layout. The feature never worked great in general (yes, I know a certain number of people will say it's great), but you need to look a the larger experience. I recommend putting a simple switch or set of jumpers to change the layout over to DC when you want. I can do this to my layout in about 5 seconds and it only cost me $7 in parts to swap in my old DC controller. I cannot agree with "MAKE SURE" you have this feature.
Also, the other side of the coin, since we have made this unfortunately more complex than Todd ever asked for (my apologies Todd) is decoders that have a DC mode, i.e. a DCC decoder in your loco. Most have this feature, but again, once you go DCC, you will rarely want to run the same loco on DC, so I do not classify this as a "must have" feature. Optional is a good term here. (I mention this other mode because often people just say "analog mode" and sometimes they refer to running a DC loco on a DCC layout, and sometimes they are referring to running a DCC loco on a DC layout, so these last 2 paragraphs illuminate both)
The point about the mts functions also bears more explanation. Early LGB decoders were "Serial", a very goofy way to control functions from the DCC perspective. Most DCC hand controllers have 10 or more "function" buttons to control functions. You push a button and the sound happens. Well, LGB did something funny, and if you wanted function 4, instead of hitting the F4 key (parallel), you hit the F1 key FOUR times.
Goofy. But, Dan implies that you cannot control all the features in such a system. "if the locos have the parallel function, you can control all the feaures."
Which implies "if the locos have the serial function, you cannot control all the features".
This is not true, you can punch the F1 button enough times to trigger the serial function on that old decoder in the loco. There are upgrades to the decoders to make them "normal" and also there are many many manufacturers of DCC decoders, so you have a lot of options here, it's not like being tied to one proprietary system, like Aristo, or Tony's or AirWire or Locolinc or ....
Now probably the flame wars will start, but I'm trying to be helpful, if you are looking into the future, it's hard to beat all the options in this method of control.