Oliver
Barry
Both
Neither
Hal and Barry is the boring friendship.
Hal and Ollie is the interesting friendship.
Same case as in Dick Grayson and Wally West compared to Dick Grayson and Roy Harper respectively.
I would say Barry for the most part. GL and Flash are like peanut butter and jelly.
Never really liked the GL/GA pairing even though that was one of the first comics I ever collected back in the day. Yeah. They both wear green. That's no reason to team them up. Ollie doesn't work well in space stories and Hal doesn't work in the more grounded world of GA.
but, Flash and GL work great in each other's settings.
Batman - Daredevil
Screw the Trinity, I want a Troika title where Barry/Hal/Ollie go on epic adventures.
That...is an interesting question.
I recall Carol meeting Barry during a double-date, but she also met Ollie during Hard Travelling Heroes (when she was confined to a wheelchair) and I think he and Hal helped save her company, so she's probably pretty appreciative of him, if nothing else.
Just shooting from the hip here... I don't remember Carol really caring for Ollie's super-Macho ways. He was always pretty brash and verbally berated anyone (Hal especially) who disagreed with his opinion. I have a hard time picturing anybody who would find it endearing to have someone chew out someone your close to. In fact I would imagine it would bug her more then it ever would Hal who just 'knows how Ollie is..."
But I honestly can't remember a specific confrontation. Barry and Iris double dated with them a bit, was a generally nice guy... and I don't remember her ever having anything bad to say about Barry.... but I honestly don't remember her mentioning him much at all...