Well, I prefer electric pump as I have a friend who is capable for adjusting it. My Transporter 2.5TDI has now about 350hp, 700Nm and next step is to get over 400hp, 800Nm out of it. To get big power out of any diesel (IDI, TDI, mechanical, electrical) is easy. To get wide powerband for everyday use is not. This is not that critical when you use these engines on a car that weights less than 1000kg, but try that on 2000kg van. And that's just when it is empty and has no trailer attached to it. I also drive my van something like 20 000km every year.
I have always concentrated on driveability and thus suffered some top power, but that's just me. Luckily enough I have a friend that is not copying others programs for TDI, but he invents something new all the time for them. He also made an electrical controlling for my VNT which had a huge difference at highway speeds (earlier >1,5bar, now 0,4-0,6 bar).
Don't get me wrong. Mechanical pumps are cool too and Mynäpump here makes pump mods for MB 3.0L IDI engines. They are getting over 700hp out of those without e-pump, but they are encountering some difficulties with rough idle and low rev area. First e-pump with Mynä mods has been just programmed and it was easy to do as old Bosch is very simple compared to modern ones. My programmer made also an electronic control for VNT on one of those MB's, but down side is cost (about 2000e with hardware and software). You can't do this with MegaSquirt.