HTH is meaningless between these two players. Yes, Federer won the last 8 matches of this match up. However, Agassi was 33-35 years old during those match ups. I wouldn't expect an all time great from ages 33-35 to win a single match against another ATG during his prime. That would be unreasonable.
Being an American, it was tough for me to choose between Agassi and Sampras. I typically pulled for Sampras. I liked his demeanor and I loved his play at the net. He was an artist. But I liked both players a lot. When Sampras declined, I started losing interest in tennis, especially when Safin and Hewitt started playing well. Roddick got me back into the sport after a layoff. Then somehow, Federer won me over even though I hated him at first. Federer was this hot-tempered kid with a pony tail that started destroying Roddick, the last great American hope. It sucked big-time.
Once Federer is out of the sport, I think that I will pull for Djoker. I've always liked Djoker, except when he plays against Federer.