is first class worth it? EWR <--> SEA

Hello! I got the United card this year and this is the first time I'm redeeming miles for a flight. I am flying to SEA to connect to Asia and on the way back, I am not taking a days rest in between (flight lands at 11am and flight back to EWR is at 2pm

I was considering doing first class but I realized these aren't layflat seats-- is it worth it to fly first anyway? or should I just redeem for regular economy

I'm a small person so the seats don't bother me aside from not laying flat (I have a bad back)