Lanark said:
That doesn't mean it's more selective, the Giro and Tour are completely different races, you can't just compare two climbs from two different races, and then conclude which climb is more selective based on time differences.
This would inevitably lead to contradictions. Is La Toussuire an incredibly easy climb, because nobody in the Dauphiné can make a difference on it, or is it hard, because in the Tour the differences are big?
Giro mountaintops:
Montevergine di Mercigliano
1 Bart DE CLERCQ (OLO) 2'54'47"
10 Christophe LE MEVEL (GRM) m.t.
Etna (Rifugio Sapienza)
1 Alberto CONTADOR VELASCO (SBS) 4'54'09"
10 Hubert DUPONT (ALM) +1'07"
Großglockner
1 José Humberto RUJANO GUILLÉN (AND) 4'54'45"
10 Denis MENCHOV (GEO) +1'36"
Monte Zoncolan
1 Igor ANTÓN HERNÁNDEZ (EUS) 5'04'26"
10 José Humberto RUJANO GUILLÉN (AND) +2'10"
Val di Fassa (Rifugio Gardeccia)
1 Mikel NIEVE ITURRALDE (EUS) 7'27'14"
10 Steven KRUIJSWIJK (RAB) +4'13"
Nevegal (CLM)
1 Alberto CONTADOR VELASCO (SBS) 28'55"
10 Vladimir MIHOLJEVIC (ASA) +1'04"
Macugnaga
1 Paolo TIRALONGO (AST) 5'26'27"
10 Kanstantin SIUTSOU (THR) +34"
Sestrières
1 Vasil KIRYIENKA (MOV) 6'17'03"
10 Roman KREUZIGER (AST) +6'16"
Here we have the follies of using the time gaps to judge how hard a stage is raced or how hard a climb is.
Simply using the time gaps, it is clear that the toughest climbs are Rifugio Gardeccia (which is only 6km long) and Sestrières (which isn't very steep). As the race goes on, the gaps get bigger. Partly this is because the climbs DO get harder as the race goes on (Zoncolan is tougher than Großglockner is tougher than Etna is tougher than Montevergine) but does anybody genuinely believe that Nevegal is as selective a mountain as Etna? Being an ITT really skews things.
As does the state of the race, of course. Gardeccia was the toughest stage of the race, but the first finisher was part of the day's break. Take Nieve and Garzelli out of it, the next 10 finishers were split over 2'39", a larger gap than Zoncolan, befitting of the stage's queen status. But this doesn't make the final climb a tougher one. It would be foolhardy to suggest that the larger gap is an indicator of the final climb's toughness, especially as the Crostis was taken out. Similarly, Sestrières' difficulty is artificially inflated by a) a much tougher preceding climb, and b) Kiryienka smoking the field by nearly 5 minutes from the breakaway. Sestrières is not a hard climb in itself; its role in a stage like that is to carve open gaps that were already there, make legs that had long since been screaming for murder force their way uphill again. It's a bit like Aprica in that respect; Aprica is not a selective climb in and of itself. But put it after the Mortirolo and see situations like 2008 where there was 9 minutes between various GC contenders there.
If you wanted to use the times taken to climb the mountain, or the time gaps produced, as a proper indicator of difficulty, then I feel like you could only really apply this in the case of a mountain time trial because that is the only situation where it is the same in both instances. And as I illustrated before, by comparing the Santuario di Ooropa and Kronplatz ITTs, the steeper, nastier climb produced much, much bigger gaps.