i'd say this highly depends on the ee on the weapon setup you got.
You do not have to stick to one system necessarily, but check if it is beneficial to upgrade or not depending on each weapons ee.
Personally, i use medium ee weapons in the low levels with nice adds but upgrade them even every 5 levels therefore, so 1, 5, 10, 15, 20.
Afterwards, i used level 25, 35, 45, and finally 55 weapons with basically the same ee,
but a very strong master quest one at the end since this is the longest period and monsters are strongest here ( especially if you plan to mf in the high levels )
The problem in your 2. suggestion is, that you have to play 15 levels from level 40 till 55.
So if you do not have a strong level 40 weapon, this 15 levels, especially from 50-55 will be a pain.
In that case it might e.g. be better to take a level 50 weapon as mq weapon instead of level 55 or buy another weapon for in between.
If you havent seen it yet, this chart can be a grand help to see how much an upgrade of the weapon can help (or not help).
http://forums.d2jsp.org/index.php?showtopic=25037040&f=272