Well, I would say that if you calculated a chart all based on equatorial directions and a chart all in ecliptic directions, they would both be valid. But to mix the ecliptic and equatorial together gets into problems. The main reason Placidus was so popular, it was the first table of houses printed in english. Although, as an aside, EH house is popular in the UK and India. Just as Vedic astrology is all sidereal measurements and there are heliocentric charts too. The key is that the system be consistent. Measurements should be apples and apples, not apples and oranges.
Which is why the Table of Houses all stopped at 66deg, at the Arctic Circle. Above the Arctic Circle as you travel to the geographic north pole, you are walking geographically north while you are walking ecliptically south. That is why the houses collapse.
Again, you can always put in the MC/IC as a point in the chart, and not give up your desire to blend the two directions. I always put the MC in the chart as a testing point. I put Chiron in there too, sometimes the Vertex to test and follow it. After 10-15 years, I'm not impressed.
If you ever get the CPT book, Astrology of Inner Space, it extensively analyzed the MC with several graphs to show the differences in measurements. In a simple example, the ephermerides lists planets in ecliptic long. You really cannot tell if a planet is really conj the MC because it is in equatorial long. It's possible to be way off from the actual planet. To be sure, then use right ascension measurements for the planet to see if the MC and planet are really conjunct.
I never attempt to change astrologer's habits and personal preferences. But they should know what they are doing in their calculations. Now it's all handled for us with software. So the past 20 years, the newer astrologers never deal with this and have no idea how these measurements are done. Therefore, they never question this either.
Robert Hand and I had a long debate for years over WH and EH. He finally said in 2010 that EH is just as valid as WH. Of course, he is CONSISTENT with teaching Greek techniques using WH.
A short story: Back in 1998-99 students of Rob's had an online blog/list where we talked and debated. At the time, it was being taught that the Greeks did not use/recognize out of sign aspects. Therefore if Mars was at 29Scop and Saturn was 1 Pisces, it did not count! Rob was saying to students that they didn't function. I differed with this concept on the list. Later, there was a strong flame war and very quickly the list was terminated under a Mars sq Uranus transit out of sign! Proof is in the pudding. I did email him and called him on it.