It's always interesting when there's one pollster that breaks from the pack. Quinnipiac is quite well regarded, they come 19th out of 538s list of 270+ pollsters when it comes to accuracy - they have the same score as Ipsos.
Yet unlike nearly every other pollster, they have Biden holding an advantage over Trump of +4 and they have had him leading consistently for over a year now. That said, they have a chequered history, underestimating Trump's vote-share by 4-5ppt for the last two elections. Whether they've corrected their methodology since, I don't know.
"A Biden-Trump split decision on physical and emotional fitness leaves both looking vulnerable. Yes, Trump wins walking away on the age and stamina question, but voters have more confidence in Biden's empathy toward them and his emotional stability to handle the job," said Quinnipiac University...
poll.qu.edu