There are many people on this forum that know far more about this subject than I do, but I'll give it a try.
Compliance is a measure of the stiffness of the suspension of the stylus. The lighter the arm, the higher the compliance of the stylus should be. This is because the system comprising arm, cartridge and stylus has a resonance frequency that should be well below the 20 Hz mark - the lowest audible frequency. (I am simplifying here - what I call "arm weight" is effective mass for example.)
The Philips arm is lightweight, and requires a cartridge with fairly high compliance. The Philips GP400 and 401 cartridges that were usually mounted on the GA312 have a compliance of 20 x 10-6 cm/dyne, the Pickering has 16 x 10-6 cm/dyne, the Audio Technica's I mentioned are around 10 x 10-6 cm/dyne, but actually hgher since Audio Technica uses a nonstandard frequency for its compliance measurements.
Cartridge data can be found here: http://www.cartridgedb.com/
Audio Technicas do not have a "warm" character. The AT 120 is the best of the two. The AT 110 is the cheapest. However, the compliance of the Pickering is the best match with the arm.
Personally, I would go for the AT 120.