Beauty is indeed in the eye of the beholder. I personally don't like the dyed ones because they are not natural, but many folks like them on their window sills. The one on the right may be a septarian nodule as Smokey says, but it may also be an agate thunder egg. There really is no definition of nice or junk ones, I find the center one quite pleasing but it's only my particular taste. I am a lapidary so I look at most agates as something to cut up and polish into cabochons for jewelry and I never used dyed stones for that purpose as I like my jewelry to be all natural. Many people collect and display the slabs like yours as specimens since there are an infinite variety of colors and patterns in agates from around the world.