Oh my...
I try to avoid becoming engaged in these "what if" debates, but my last five minutes of reading has been rather "interesting", so I thought I'd interject.
First, tanks aren't necessarily dedicated to taking on other tanks. We train(ed) and operate(d) in combat teams for a reason. In the offence, for example, tanks accompany the infantry onto the objective to provide intimate support, digging the trenches out with the grunts, blasting bunkers and providing overwatch against counterattacks. Only after the infantry has secured the objective to the tanks peel off to form the "ring of steel" to protect against armour-drive counterattacks.
Also, on the offence (say, during an advance to contact), tanks would lead, simply because tanks are capable of taking on the widest variety of potential threats - other tanks included.
The point of this post is to remind everyone that tanks have
never operated alone - they're always accompanied by infantry, who will lead depending on the tactical scenario. A combat team, with attached engineers and FOO, is perfectly capable of conducting operations in a very wide variety of tactical scenarios, including against the "snakes" in an urban setting. We should also remember that we can have infantry-heavy or armour-heavy combat teams, again dependant on the scenario.
Do we need three full regiments of tanks? Probably not. However, we do need a mix of capabilities that provide the leadership with enough flexibility to accomplish a variety of missions - from invading Iran to peacekeeping in E. Timor.
Typically, I steer away from academic discussions of tactics (and of Jane's book-type discussions of shiny new kit), primarily because tactics are extremely dependent on the actual scenario on the ground and will certainly be adjusted to suit highly individualized situations. However, we have perfectly force structures to employ in 90% of instances, along with the doctrine to accompany them. Fallujah isn't
that different from Ortona, after all...
T39, jockeying now...