The advantages of +30/x10:

- You can just look up the mass of an object on the KYoS table and convert directly to a toughness rating. A 1 lb unliving object (KYoS -3) has 4 hp (LogD 18). A 1,000 lb unliving object (KYoS 27) has 40 hp (LogD 48).
- It interacts nicely with the range/speed chart. For example, if you want to divide damage by distance, that's just a modifier of -10 + 5x range modifier. If you want to multiply by speed, add 10 - 5x speed modifier (e.g. collision damage for an unliving object in KYoD works out to 3d + Mass - 5xRSM - 23). You can do the same sort thing with the +20/x10, but you wind up multiplying by 10/3, which is annoying.
- In the typical range of PC HP (8-18) you can just add 20 to the linear value and be correct within error margins.

The disadvantage, however, is that GURPS 4e did a lot of things based on quadratic scaling, and in vanilla GURPS lifting ability actually varies with 2/3 power of mass, so a 1,000x heavier creature (with 10x the ST) actually only has 100x the BL (+20). The collision case is particularly inconsistent because you can get 10x damage by either multiplying speed by 10 (100x the energy) or by multiplying mass by 1,000 (1,000x the energy).

The thing this is leaving out is mostly wound width: the 1,000x mass collision might make hole of the same depth as the 10x speed collision, but the hole is much

*wider*. The only attacks in G4e that have a concept of wound with are piercing attacks, but it actually applies to everything. In the case of ST-based attacks, a 1,000x more massive creature might not apply 1,000 the force -- but it probably applies 100x the force over 10x the distance, for a net of x1,000 energy.