I did a LOT of shopping around last year when my son and I decided that we wanted something a little better than the 6" we had looking to the future with him wanting to get into segmented bowls. After reading all of the reviews I could find on all of the available 12-inch models I finally decided on the Delta 31-140 12" 1/2 hp - got it from Amazon after comparing prices and adding in shipping, taxes, etc. I like the cast iron table, trunnion angle setting, dust collection, it even comes with the tools for adjusting it and has a place to store them on the sander. There were a lot of reviews talking about discs that were not flat or made cheaply with a lot of run out and the Delta seemed to have the least problem there, too. I also liked the manual brake on it - don't have to worry about grandson or great grandson walking into the shop and putting a little finger to a spinning down disc.
I'm not saying that is the one for you to get. You have to look and see what options each one has, read the reviews on it (from more than one source if possible) and decide what features you want for the tasks you think you will want it for. The Delta fit for us, the Harbor Freight could be a much better choice for someone else. And if you are only going to be truing up pen blanks, a 6" should be more than adequate.
Hope this helps more than confuses.