Max durability repaired also depends on the durability of the weapon used, so since 2 handers have high max durability, they also repair more. However, this honestly doesn't matter for the most part. Durability is really an issue in only 2 situation: when you have very low max and when you plan to enchant something. Anything with 10, or 15 if you want to be conservative, or more max durability will last long enough that it stops mattering. Even if repairs were only 20 points, that's the same 20 points any other ego would get and would last just as long (or even longer). There is no need and no benefit to keep maxed durability constantly. The higher max durability only allows you to wait longer for repair or to do the repair faster without wasting points. when it comes to enchanting, this simply doesn't apply to spirit weapons.
On the subject of their power, ego weapons still have, even with special upgrades, fomor and demonic weapons, the highest potential. An ego will be better than a fully upgraded weapon, excluding special upgrades, in the high 20s or low 30s levels and easily surpass even fully special upgraded weapons at higher level, unless you go for the red upgrade stones... but those are always inferior to blue with a 2 hander since the extra damage they get from blue will always give better results with crits than even the red upgrade does (not paying attention to balance you said?
). That is on top of other bonus you can't find from normal/special upgrades; like injury rate, higher balance/crit without any reduction to damage or anything and spirit weapon awakening skill.
The cost and time to get an ego to such a level are the only real issue and pretty much the only reason I still haven't made a decision. Repair costs aren't a huge issue if you don't rely too much on the weapon.
On another note, yesterday was a pretty productive day in term of dragon hunting. I was able to take part in the killing of 3 white dragon on channel 1, 2 and 5; earning about 5k, 3k and 6k contribution respectively. Each of those also gave a single demonic piece plus some random junk, including a rather colorful wizard suit for woman that was thrown Laur's way. Apparently, white dragon is of neutral element, which is what lead to the current consideration into turning my HLC into an ego as it has a level 2 ice reforge granting about 20% extra damage against anything not of the ice element.