Um, yeah, XI_Legion, lighten up. The guy asked a reasonable question, no need for that tone.
Warspite, I understand what you're saying- yes, Pz-IVs in CMBB can die with frightening rapidity in late war scenarios, and if you're up against enemy armor and you DO have a choice (which the Germans in the war didn't), I would agree with you and take 4 Tigers over 8 Pz-IVs.
In early/mid war engagements if you have a mix of Pz-IIIs and Pz-IVs, it's useful to lead (if on the advance) with the Pz-IIIs for the reasons you've stated- they can take turret hits that the IV can't. And if you let the Pz-IIIs be the targets, while your L43 IVs are the real shooters, things can work well.
If you're up against significant infantry, however, I'd lean to the IV over the III. The III's 50mm gun isn't terribly effective against infantry, especially if you want to take buildings down.
And even though the III can be as effective or more getting penetrating hits (especially compared to 75/L24 IVs) because of the higher ROF and accuracy, don't forget that Russian tanks will all too frequently shrug off a 50mm penetration with no damage.
Basically I treat L24 IVs as turreted assault guns, primarily for infantry support. Mid war, with late model IIIs and L43 IVs, it's a tossup. The IV has a much better gun but dies more easily. Late war, again yes, the IV has to be used quite carefully against 85s to be successful.
At least that's been my experience.