I know that Zahi Hawass gets pretty irritated with the suggestion that the ancient egyptians weren't smart enough to figure out who to do these things on their own. Suggesting that it was aliens sends him round the bend.
Oh, I'd wager the ancient Egyptians were plenty smart enough to build the pyramids with either technology. The modern Egyptians, however, are certain evidence of de-evolution. Stupid and degraded are two adjectives that come to mind.
Zahi "Zowie" Hawass also has claimed that the number of stones in the Great Pyramid (Khufu, a.k.a. Cheops) is more like 500,000, compared with 2.5 million which is commonly believed, or more than (I think it was) 4 million calculated by someone writing in KMT a few years ago. Hawass also claimed that the size of the stones is something like 1000 pounds each, instead of 2+ tons as is commonly thought.
The logistical problems of dragging 2 1/2 ton stones up sand ramps (one wrapped around the whole structure, or whatever), plus the stones which are much larger, plus the now-missing facing stones (stripped by some caliph during the Middle Ages) in the 20 year time frame attributed to its construction creates these kinds of problems.