From my experience the hauppage is the best.
I originally got the Dazzle Plus and let me tell ya. That thing is a peice of crap. It does not even cime with all of the materials needed to capture. I had to buy about 40 dollars worth of splitters and cables. It is easily able to cost over 100 bucks and it took me hours to set up. Then you can not even get HD on it.
The Blackmagic is a very good capture card but like said above you need to have a fast computer. My computer was not that great so I avoided it.
The Hauppage is amazing. The software is very easy to use and it sets up for HD in 10 minutes or less.
A good piece of advice for all of you is if you are recording save your file in AVCHD if possible. This will make it so you can put that file directly onto your video editing program. If you are looking to upload straight to youtube then do MP4.
If you have any questions about cables and set up for any of these devices please message me. I have pretty good experience with cables from working with my video broadcasting group at my school.