Here's a short summary of the main ayanamsa groups from astro.com for those wondering into what category/tradition Wilhelm's ayanamsa could fit:
Dhruva Galactic Center Middle Mula Ayanamsha (Ernst Wilhelm)
This ayanamsha was introduced in 2006 by the American astrologer Ernst Wilhelm. The galactic centre is projected on the ecliptic in polar projection, i.e. along a great circle that passes through the celestial north pole (in Sanskrit dhruva) and the galactic centre. The point at which this great circle cuts the ecliptic is defined as the middle of the nakshatra Mula. This ayanamsha is very close to the Usha-Shashi ayanamsha and the Revati ayanamshas. With all of them, the star Revati (ζ Piscium) is near the sidereal position 29°50 Pisces. This ayanamsha is a little less stable than the other ayanamshas. Since polar projection is used, it is a little bit influenced by general precession. However, polar projection was actually the method used by the Suryasiddhanta. It must be noted that Wilhelm uses this ayanamsha only for the definition of the nakshatra circle not for the zodiac, because he uses the tropical zodiac combined with sidereal nakshatras.
This looks like Lahiri is the odd one out after all.We have found that there are basically five definitions, not counting the manifold variations:
1. the Babylonian zodiac with Spica at 29 Virgo or Aldebaran at 15 Taurus:
a) Fagan/Bradley b) refined with Aldebaran at 15 Tau, c) P. Huber, d) J.P. Britton
2. the Greek-Hindu-Arabic zodiac with the zero point between 10 and 20’ east of zeta Piscium:
a) Hipparchus, b) Ushâshashî, c) Sassanian, d) true Revati ayanamsha
3. the Hindu astrological zodiac with Spica at 0 Libra
4. ayanamshas based on the Kaliyuga year 3600 or the 23rd year of life of Aryabhata
5. galactic ayanamshas based on the position of the galactic centre or the galactic nodes (= intersection points of the galactic equator with the ecliptic)
1) is historically the oldest one, but we are not sure about its precise astronomical definition. It could have been Aldebaran at 15 Taurus and Antares at 15 Scorpio.