Averages don't do justice to a player.
Both Dhoni and Matt Prior average the same in Test cricket.
Are both of them equal as batsmen in Test matches?
Hell no. Matt Prior is twice the test batsman Dhoni is.
There is a reason why Samaraweera and a few other 50 averaging aren't rated as high as ATGs are rated even though all of them have similar averages.
Its NOT just because of overseas Tests. Some of the 50 averaging batsmen have very good overseas records but STILL aren't rated as ATGs.
Why so?
Its because what matters is crucial knocks.
I am not talking about knocks where you win the match. That is dependent on bowlers but crucial knocks is different.
Crucial knocks that will setup games or win games or where you valiantly fight BEFORE the result of the match is a foregone conclusion. Of course, if you are team is beyond hopeless, great knocks where you valiantly fight get noticed. Eg - Dravid in England 2011
Take Kohli for example.
Has a good average in NZ but NO crucial knock that really helped the team. Its easy to score a century in one of the games where the result is already known. Stats will say he had a successful NZ tour. I would say if Kohli had got 3 ducks and scored in the first Test (last innings) taking India to victory, people would have rated Kohli more. Rahane, on the other hand, scored a brilliant ton to setup a win which our bowlers blew. He was hailed.
Another example.
In ODIs, Umar Akmal averages MORE than Yuvraj Singh.
Will any neutral fan say Umar Akmal has performed better than Yuvi?
Hell no. Why? Cos when needed Umar Akmal goes missing (more often than not). Yuvi on the other hand delivers.
If Umar in important matches where his team needed him, he would have been hailed a brilliant match winner (with the same 38 average and same amount of runs).
I am not a big fan of using blind averages to judge players.
Dhoni, apart from his recent England tour, has done didly squat in overseas tours. In SC, he has been a very good batsman. But to call Dhoni an under rated batsman is wrong. Dhoni is ANYTHING but under rated. Be it Tests or ODIs. He is rated perfectly.
As for comparison, its an absurd one. Both play a different role for their teams which makes it very hard to take a pick.
Dhoni isn't reliable as a Test batsman like Misbah but he can blast off in the end if given a platform.
Purely judging batsmanship, I would go with Misbah.
In SC, Dhoni usually comes in at the end to smash a few. If Indian team had a weak batting, Dhoni's average would have taken a big hit.
Misbah wins.