A lifecrafter who invests heavily in spells, and an infiltrator who invests more in Int and creations, are very similar.
IIRC, the lifecrafter only starts with 1 more Int than the infiltrator does. The essence multiplier is more significant, but not hugely so, and the infiltrator does have better return on skill points for magic skills.
The infiltrator will be a little hardier, which can make her a bit more flexible. The extra bit of essence for the lifecrafter can on the other hand give him a bit more brute offensive power.