What the consolidation of unit strength into a single value has done-most of all-is to eliminate the ridiculous anomoly where, if you had two identical units going against each other, who would win would almost always come down to who 'attacked' and who 'defended' (given the time scale of turns, this in itself is a ridiculous concept-battles tend to be massive free-for-alls, where a seperate attacker/defender simply doesn't exist).
For instance, if one tank attacks another, you could bet your life the attacking tank would win, because its Attack Strength was way higher than its opponents defense strength. Now, two tanks will have an even chance of winning-all other things being equal. It also removes the need for artificial designation of 'offensive' or 'defensive' units-given that almost every unit in history was actually used to do both-though it might be more effective at one or the other.
Which of course brings us to the point already raised, which is that individual units will be specialised in their attack/defense against certain units and/or in various terrains. If you ask me, the combo of a consolidated combat score and differential bonuses/penalties in specific conditions, you allow for a much more realistic and flexible combat system-one far better than that of Civ2 or Civ3. Of course, those making the complaints would realise this if they actually read the entirety of the available info-and not just the stuff which they can spin into the most negative context possible (something which I believe was done quite a lot in the transition from civ2 to civ3 as well).
Yours,
Aussie_Lurker.