One of these unprocessed 100% center crops (straight from DPP, 7D) was taken with a 400 2.8 IS + Canon 1.4x TC II (560 mm).
The other used a naked 500 f4 IS. Both were at f/4 and ISO 200. Each crop is the best of three RAW shots, Live View contrast detect AF, remote switch, 475B/516 support.
The 560 mm shot was taken a bit farther away to equalize field of view. Can you guess which crop was taken with which lens?