If you want to compare a long-rest warlock vs a short-rest warlock, why not use the RAW version of both.
For example, a RAW long-rest warlock would have either at-will abilities or long-rest abilities. For example, Mage Armor and Bane. A purely short-rest warlock would have at-will abilities and regular spells. Honestly, they don't look too different, but the long rest one ensures they have access to spells that capitalize on their limitation and at-will capabilities that don't rely on resting at all.
Which one is stronger is up to debate. Personally, though, I'd give it to the short-rest oriented warlock.