As the "Safelstran man" here, I have played with ALL the versions and can give you a nice account of the four variations (I'll not count RQ4 in although it has its merits). To avoid confusion, I'll refer to Sorcery as Malkioni Magic, as BRP's Sorcery is the equivalent of Divine Magic in RQ.
Original RQ3: a sorcerer in RQ3 was in fact the weakest of magicians, and required 100+ stored Power Points to be viable. His role was just that of the supporting character who used to cast long-lasting spells to enhance the party's characteristics, as it took him two melee rounds to cast a spell that could disable an opponent, whereas a simple Befuddle acted in two strike ranks. Skill only affected how many times you had to retry before your spell worked, and an Adept without a decent array of Intellect Spirits was even weaker than a beginner due to the flawed Free INT rule (yes, RuneQuest had flaws, too
)
RQ3 with errata (or Games Workshop): the revised Multispell rules finally made Malkioni Magic superior in combat to other magic systems. A powerful wizard was able to take down a squad of men with a single spell, and this was more fun to play.
Sandy's Malkioni Magic: this was intentionally aimed at Glorantha, and worked decently. You have to introduce a new score for characters, Presence, and this requires additional bookkeeping, but your power is now connected to adherence to some principles ("vows"), which is more Malkioni, and skill at casting, not Free INT. I used it for Henotheists and Stygians as secondary cult magic instead of Spirit Magic and it worked fine, as players were forced to roleplay their cult vows to get more magic. Sorcerous Humakti with permanent Damage Boosting on their swords are .... scary
Warning: do not read further. You might not like what you read.
You were warned. Especially the One who Breeds Amphibians.
Mongoose Sorcery: it is by far the best incarnation of RuneQuest Malkioni Magic, if you accept the fact that a half dozen spells are totally botched and need total rewriting. A wizard reacts faster than a theist magician, and once he reaches a good skill with magic he can cast devastating spells
at a cost of one or two Power Points, plus cantrips for zero Power Points. This is the first BRP magic system that allows you to have a powerful magician that does not rely on external Power Point sources. This is The Way it was Meant to Be.
(waits for the people with the tar and feathers)