Regen has a lot of issues design-wise in that it can completely unbalance the player's resources if there is a good place to hide.
Health packs force resource limits on the player, which is in theory better design, but has the often unfortunate consequence of potentially putting the player in a position where they are far more resource-constrained than the designers intended.
The best system would limit player resources in such a way that they are strictly limited but completely predictable to the game's designers. Health that completely recharges once a set of encounters and/or obstacles is cleared, but does not refill at all in-between is the best way to go, but I can't really think of many games that do this.
Health packs force resource limits on the player, which is in theory better design, but has the often unfortunate consequence of potentially putting the player in a position where they are far more resource-constrained than the designers intended.
The best system would limit player resources in such a way that they are strictly limited but completely predictable to the game's designers. Health that completely recharges once a set of encounters and/or obstacles is cleared, but does not refill at all in-between is the best way to go, but I can't really think of many games that do this.