I saw that stat before and have to say it is pretty impressive. However you have to factor in the division. Plus there is more than just the win ratio as the mark of a good manager. There the sucess factor (promotion primarily, staying up too, cup runs etc). There is also circumstances and what they had to work with. For example if you look at Kendall and Spackman's win records then the latter is ahead. However I would rate Kendall as a much better SUFC manager than Spackers. Kendall took over a team that was destined for relegation, kept them up, turned them around and got them playing good football very quickly. He then went on to get the team (on a pretty low budget) to the play off final. Spackman took over a team that was pretty good, quite confident and was given plenty of cash to play with (although he did have the rug pulled from under him a bit later).
What Basset achieved on a shoestring is absolutely incredible. Warnock's record is pretty impressive too. Especially when you factor in that he was never given any money (until 2005).