I would add that in my own particular situation my 2 pcHDTV CAN cards (with Generation 5 LG DT3303 tuners) perform a bit better than my 3 USB devices (2 950Qs with Xceive XC5000 tuners, and a single 950 with Xceive XC3028 tuner) so clearly there are many considerations at play when comparing.
All of those devices use silicon tuners and/or demods, so no surprises there. Though it would be very interesting to know what is inside the "can" on that pcHDTV board. The LG DT3303 is not a tuner chip --> it's a demodulator/decoder chip. It is often paired with a silicon tuner
such as the Xc3028 inside the "can".
A "can" tuner, in the sense that the quoted articles use the term, refers to a sealed metal enclosure (the "can"), containing tuner circuitry built up from many discrete, and mainly "analog", components. Lots of hand-tuned chokes, coils, and variable capacitors/inductors, op-amps, individual transistors, and the like.
The volume inside the "can" is often mechanically divided into several shielded sections for different stages of the RF receiver circuitry.
With a silicon tuner, nearly all of that stuff just "goes away". There may or may not still be a (much smaller)
"can" enclosure for the tuner chip and its pre-amp, but that's not a "can" tuner in the sense used in the articles.
Look at an HVR-1600
card, for example. It has a large, traditional analog "can" tuner at the top, and a much smaller "can" between that and the PCI edge connector. That second, smaller "can", holds the silicon tuner chip, and possibly the demodulator chip, plus glue, for ATSC reception.
One of my PVR-250 cards (traditional analog "can" tuner)
had trouble receiving the analog PBS station we used to get here. I pried the lid off of the "can", and adjusted some of the coils until reception was near perfect.
With a silicon tuner, that kind of issue shouldn't happen, but if it did, a software adjustment would be how it would get corrected.