To be honest, I try not to compare them too much anyway. I have both installed and play both.
They were released over 2 years apart, involve completely different forces, technologies and in very different theaters of the war. The graphics, IMO, are too different to even be comparable, and the technologies (eg. air warning radar from the very beginning for SHIV, at least if you start the war with a Sargo class boat) make tactical comparisons difficult (in SHIV, I simply do not worry about air threats as I always have ample time to dive out of danger, while in SHIII it is often the single biggest threat I have to be concerned about). Navigation is often a much bigger issue in SHIV then in SHIII as well, simply due to the nature of the operational area (eg. down off Indonesia or Malaysia or the Celebes sea - or try operating on the Sunda Shelf or Java Sea).
And I would not rate SHIV, 1.4 as bug-ridden - it is simple not that laden with flaws to warrant that term. The 1.4 patch with TM 1.7.5 and a few other mods is an very enjoyable game.
As is SHIII with GWX2 - I give 'em both a
