If either of them is in my team I would be lucky!
Personally I like Messi more and I miss those days when the team was built around Messi. It was really exciting to watch super stars around Messi; Xavi-Iniesta, Henry, Villa, Zlatan, Neymar... He always adapted himself.
They won all 6 trophies in one year. Messi scored 50 in one year, great times. Now Barcelona is a mess.
Both players are real professionals and play at the top level even at their age. Ronaldo was born in 85, Messi in 87, they still have time to play, Messi has probably more.
Ronaldo looks stronger and have more strength but stats say there is no big difference in performance. Messi is fast with ball, his pace and acceleration is incredible when he dribbles. Because he plays only in Barcelona he knows very well the tiki taka game and he creates chances for his teammates too. His assist stats also show us that he's an all around player.
Ronaldo proved himself in different leagues, accepted every challenge and got championships. I respect that. I feel like he'll do one last challenge after Italy adventure and dominate a smaller league, maybe Portugal or Turkish league before retirement.
We are lucky to watch both legends live.