I would be curious to see what the evidence from Widewing says about P-51/P-47 comparative turn rates.
My impression from reading all the combat reports on Mike William's site, is that the P-51 turns better than the P-47 at low speeds, 220 MPH IAS or less, if using flaps, and it can certainly out-accelerates the P-47 in a wider turn.
At most usual combat speeds however, it clearly cannot out-turn the paddle-blade Razorback P-47, and in tests the German considered their captured early Razorback P-47D to be capable of significantly out-turning their 109G-6s. They make no such mention for the P-51B, and considered it's stall problematic... Note however that later bubble-top P-47Ds seem to perform noticeably less well in turns than the earlier Razorbacks, but still could hold their own against late '44 109s, if barely.
Against the 109G-6, the P-51's turning contests can last for ten minutes at a stretch (!) as long as the G-6 can spiral downward. Near the ground the superior turn acceleration of the P-51 gains it the upper hand quickly, unless the fight takes place in very late '44, where the acceleration in turns of the later 109s seems to get noticeably better, and turning fights resume going on forever... 10-15 360° turns are very common with P-51s, up to ten-fiften minutes(!) being reported.
Against P-47s, especially in the first half of '44, a very good 109G pilot, or group of pilots, will last 2-3 turns against a P-47D, before hurriedly calling it quits and breaking out of the turn... In line with German tests results for the Razorback at least, except that in right hand turns the P-47's margin seems to vanish... For some reason, right hand turns seemed a lot less common in combat.
The FW-190A, on the other hand, easily matches the paddle-blade P-47, and gets better in later '44, just as the P-47 gets worse. Both Russian and German tests agree on the FW-190A's turn being generally superior to the 109G, maybe even equalling the F, at least below 20k. This was probably accentuated on two wing gun 190s compared to four wing guns variants.
The most confounding thing I have found about the P-51, in reading 700+ P-51 combat reports, is the unreliability of its guns all the way through 1945, including on the D series... About 1 in 6 reports is affected by it in some way, sometimes the violent maneuvering leaving but one of six guns hammering away... The more violent the maneuvering the more jams, so especially prevalent against the 190... On the B model the problem takes on truly epidemic proportions, one being equipped with experimental field-made pneumatic "chargers", the pilot reporting unjamming his guns six times in the course of two 360° turns...
The P-47? Almost no jamming reported in 6-700 reports...
On that basis alone, as a U.S. pilot, I would RUN from a P-51... I guess the experience of firing live guns during hard-turning combat was not so prevalent in late '44 to taint the Mustang's reputation...
Gaston.