I agree with elpaso96.   I don't believe Redbubble has a particularly strong moat, and things can rapidly go pear shaped for them if for example, Google decides to adjust their search algos, as happened a few years ago.   

I prefer CTT over RBB atm.  Higher value spent per customer - luxury good svs shitty t-shirts, and CTT seems to be undercutting the entire market and stealing market share at a rapid rate....