If the Smolensk disaster was to be traced down to a single decision (other than attempting landing in the first place), it would probably be the choice of radio altimeter to control altitude over a very unfortuitously shaped terrain (a wide valley, with steep slopes). This made the airplane to descend to 80 meters above the bottom of the valley, instead of 80 meters above the runway located 60 meters higher.
Someone mapped the black box recordings of the navigator's altitude readouts to speed and terrain profile, interpreting them as barometric altimeter readouts and it came out as an unreasonably bumpy ride (the orange line). I tried to follow up with mapping these same readouts at the same intervals, but relative to ground surface - treating them as radio-altimeter readouts - and it follows the blue line; judge for yourself which can depict a large passenger plane trajectory more accurately.
An unbiased comparison would include both advantages and disadvantages of the two types of altimeters. In this specific case (unknown, uneven profile terrain) the one main disadvantage of the radio altimeter is obvious: it doesn't provide accurate information about altitude of the airplane relative to the runway. I wonder though, what redeeming properties does it have - what are the advantages (if any) of using a radio altimeter over a barometric altimeter during landing - any inherent flaws of the barometric altimeter, like accuracy, reaction speed, or such, in which one type excels over the other?
(yes, I'm asking for a biased comparison; one with focus on superiority of one of the other. I realize both have their correct applications, both have strengths and weaknesses, applications where one or the other is better. Here I'm specifically asking for one side of this argument; half of the full image; look at it not as "why is A better than B" but "which traits of A are better than B")