I love RF products, but I would have to say the DC is more beast. Just raw power over the RF.
T-600.4: 100x4 @ 4 ohms, 150x4 @ 2 ohms, probably a little underrated.
DC 175.4: 175x4 @ 4 ohms, 250x4 @ 2 ohms, also underrated.
Looking at the pricepoint, its an easy choice.
I have used both btw.