Lighter is better to my way of thinking, so I will take my Eureka Spitfire 1 (solo) in the future. It is quite adequate for me. I typically am either reading or sleeping if I am in the tent so I don't require much space. I only take in my handlebar bag, whatever I need to sleep, and clothes for the morning. The rest stays in my panniers and the panniers stay on the bike.
I have used my MSR Fling (two person tent) both solo and with my adult daughter. It was fine for two and bigger than necessary for one.