I myself have used both modems. There is only one potential "issue" with the firmware to be noted if you are planning on using this modem on the Rogers infrastructure on a TPIA. Some of these modems (such as my Thompson DCM-476) are equipped with an older firmware. In most cases (such as mine), the "older" firmware doesn't cause a problem, however you must be careful to note this if you have a problem that Rogers needs to examine.
I was fortunate in my case when I had an RF signal issue on the line because the TekSavvy rep that I was speaking to actually knew what he was talking about. In cases where problems exist if you have the "older" firmware, Rogers is known for blaming the problem on "unsupported firmware", even when the firmware has nothing to do with the issue. You can find more details on that in this forum thread.
Aside from this "alleged" issue with the firmware, my experience says with either of those modems that the firmware is not an issue. For me, both of those modems (Thompson DCM-476 & Motorola SurfBoard SB6120) both worked flawlessly.