Just that your question was a bit more specific and probably deserved a thread of it's own since you're asking for advice rather than giving a recommendation (the latter I think was the original intention but it seems to have gone a bit stale and possibly not developed as intended).
Anyway, back to your question... it depends what you want from the tyre. 215/40s will have a bit more grip and slightly sharper turn in, 205/45s will ride slightly better and will likely have less aggressive breakaway characteristics as the lateral G's will be fractionally lower when they do let go.
My experience here is going from 215/45/17s to 225/45/17s and 215/60/16s to 225/55/16s on previous cars (Impreza and Forester XT) and 205/45/17 run flats to normal tyres on a Mini and with the Yokos on a Lotus Elise. Going to the wider lower profile tyre on the Forester was beneficial in terms of steering response but that car obviously had much taller side walls so the effect was possibly more pronounced. Grip was improved both times when going from 215 to 225 wide tyres. Ride was improved dramatically on the Mini when changing out the run flats.
Considering you are going from run flats to non run flats, the extra stiffness from the lower profile sidewall of the 215/40 tyres may be beneficial. However, personally, I don't find a lack of steering response to be an issue on the Mini and I didn't find I lost any real steering response when I made the switch to normal tyres on my previous MCS but it did ride much better so once I've killed the run flats on my current MCS, I will be swapping them for a 215/45/17 tyre to gain a bit more grip and improve the ride at the same time.
But, like I say, it depends on what YOU want from the tyre in terms of altering the ride and handling characteristics of the car but in any case, the Yokos are a great tyre and would suit the car well in both sizes you mention as well as the 215/45/17 size (which is the one I'd go for).
Now: 2005 R52 MCS
Plus: BMW X3 3.0d, BMW Z3 2.8, BMW F700GS, Vespa ET4 125
Was: 04 R52 MCS, 06 R53 MCS