Though at different times, I've have had the SE versions of both setup in my room, with the same gear behind them. Note that the Yorkminster SE doesn't have an equivalent in the new GR line, and thus may be considered discontinued.
In both cases, the speakers were basically new, with few hours. The Yorkminster SE was first, on audition/loan. I was looking to upgrade from the Kensington SE. The bass -- quality quantity, and extension -- were all significantly improved over the Kensington. This is NOT subtle. Treble quality was very similar between the two, as it should (same tweeter). In the midrange, clarity and detail were similar. However, the Yorkminster had what I'd consider a slight hardness (perhaps a mild boost somewhere in the upper kHz-4kHz region). The Kensington has a lovely sweetness in its mids that was absent in the dryer-sounding Yorkminster mids. That's not to say the Yorkie mids were bad -- it's just a matter of preference. My local Tannerd buddy absolutely loved the Yorkminster from top to bottom (at least sonically; neither of us love that Teak finish), and he's got better hearing than me.
Though I thought some of the midrange flavor might be attributed to lack of break-in, I decided it wasn't worth the risk to upgrade, and set sights on the Canterbury SE.
When I got the Caterbury SE (purchased outright), it was clear that this was a darker sounding speaker than both the Yorkminster and Kensington. It can even edge into "wooly" territory in the wrong setup. The midrange is far more akin to the Kensington (i.e. sweeter), which I was relieved about. However, I did find myself making tweaks/adjustments to bring out the presence and treble regions (e.g. +1.5dB treble shelving in the crossover panel, went from Mullard to Telefunken 12AX7 in amps, etc). The bass is more powerful and effortless compared to the Kensington, but it doesn't really delve much deeper like the Yorkminster does (the spec sheet is quite accurate here). The Canterbury excels in scale; images are bigger and more life-like than with the Yorkminster and (especially) Kensington -- this is displayed at it most spectacular with large orchestras. I noticed that break-in didn't change these characteristics; it only made the speakers more articulate over time. This leads me to believe I made the right choice over the Yorkminster. That said, the Yorkminster should be viewed more as an alternative than as a step-down to the Canterbury. If you don't need sweetness in your midrange, then the Yorkminster may be the right choice -- it certainly extends deeper in the bass, though make sure you have enough room to handle that. It can also prove to be troublesome to poorly isolated turntable, or a table with any amount of rumble!
