2009 world champion Button has an unique vantage point on assessing two of the very best drivers in F1, having shared the McLaren team with Hamilton in 2010-2012, and with Spaniard Alonso with Honda power this year.
Hamilton, now at Mercedes, is the sport’s new and ultra-confident triple world champion, but Button said in Abu Dhabi: “Fernando is an incredibly complete driver in the race.
“For me he is a greater challenge than Lewis,” he is quoted by Auto Motor und Sport, “because he never gives you a second of rest, whether he’s in front of you or behind you.
“With Lewis, there are days when he is invincible, and then at the next race you wonder ‘Where is he?'”