I have a 46" TV that I play on now.
I was playing on the 19" screen in my Gaems hardcase until a few months ago.
Ask a professional gamer(which I am not) and they will tell you smaller is better. After playing on both, I would agree but still prefer the 46".
If yiu NEED a tv then get a tv that suits your room or whatever, but I'd recommend getting a gaming monitor. I got a 27" monitor with great specs and 2 hdmi inputs with 1ms response time for like 250 on amazon. Best investment I've ever made for gaming. I have a 50" and a 42" in my room as well and won't ever hook my console back up to them so I use my 50" for cable and my 42" as a computer monitor