The reason a filtered faceplate is a good idea is because you don't want to be sending the VDSL2 signal all around your extension wiring. With the filtered faceplate, the filtering is done at that point so all your telephone extensions are already filtered. The exception of course is the cable to the modem. It can either plug into the top port of the master socket (unfiltered), or can be internally connected to the AB terminals inside the master socket (in the case of modem extension wiring where you want it to look neater).
The drawback of separate microfilters is that the VDSL signal is going around all your extension wiring, which can be lossy at VDSL frequencies. So your signal is more likely to be attenuated, which translates to slower speeds.
The other drawback is just that some microfilters are poorly constructed and don't do a good job of filtering.
As Terranova667 correctly points out, your setup with the microfilter is working in that you are getting close to the top end speeds. You must be fairly close to the cabinet. The only gain that may be possible by changing to a MK3 faceplate would be that it might increase your upload speed. That is purely conjecture, as it is hard to tell if it would improve or not.
If you have a lot of extension wiring in your house, and use microfilters at each extension, then you may benefit from the filtered faceplate. There are no absolutes unfortunately other than to say that generally, filtering at the master socket is better than filtering at each phone extension.
