The con of vdrop comes when you overclock and had to overvolt. So for example, my old e4500 needed 1.34v to run 3.1Ghz. but that's the VID needed, not necessary the actual power fed to CPU. Different boards have differing vcore to achieve this, and some do better than others (due to quality of design and components). With my Abit IP35-E, 1.34v VID at load is actually a vCore of 1.288v (reported by CPU-z). This is a pretty big drop. With the better designed Abit IP35-Pro board, the same 1.34v VID results in a load vCore of 1.31v. So you see the Pro is a better board than E, at least in how the power is efficiently fed to CPU.
Things like load line caliberation probably further helps to reduce it, but it may simply pad the vCore to make it look like it's not as bad. So if this is the case, with 1.288v as real vCore, your system may not be as stable as when it's 1.31v, even though you told the motherboard to feed the same 1.34v VID to the CPU. So to remedy this, what you can do is to manually set VID as 1.36v, so the vCore at load would be increased. Of course, that means your CPU is subjected to higher vCore when it's not at load. This could negatively impact the CPU's longevity. So basically the better board design, the less of an offset you need.
Both P5E Deluxe and Maximus II have 16 phase power. I think the main difference is in the BIOS ability to handle more detailed spec for Max II. Also there are some built in features for factory set overclocking in Max II. But fundamentally, both boards are pretty high-end and should do as well as any P45 boards can do in terms of distributing power.