GURPS characters become more survivable in many ways. They include:
- Buying up combat skills, for better parries and/or blocks.
- Buying up Speed, either directly, or via HT and DX, for better dodges, and going first to take opponents down before they attack you.
- Using tactics and the combat system more fully, for retreats, deceptive attacks, hit locations, and so on.
- Buying advantages, such as Combat Reflexes, Enhanced Defences, Luck, Hard to Kill, and so on.
These seem to be the same kinds of changes that get rolled into increasing D&D hit points, just specified in detail.
Buying extra GURPS hit points is not often an effective way to become tougher. I've done it exactly once, in a high-tech military game where there's no worthwhile armour, and the opponents' usual weapons are rifles doing 7d damage, average 24.5. I noticed that having 13, rather than 12, hit points considerably reduced the odds of needing to make a death check after being shot once. I'd need to take 26, rather than 24 points, to force a check. I had to accept that after taking that sort of damage, I'd be out of the fight.
The effective way to avoid getting hurt under GURPS is not to get
hit. Accepting that you will be hit regularly and trying to win a battle of attrition is not an effective approach.