why when i press tab it's more fast to scroll items by arrow keys, than by TAB ?

[RusAlex]

?

[ervandew]

How much slower is using tab than the arrow keys?
Is this true across the board for you or only when there are a lot of completion results?
Is this a problem for all types of completion (keyword, omni, etc) or just some?
Do you have other plugins mapped to the tab key as well (:verbose imap <tab>)?
What OS are you on?
What version of vim are you using?

The arrow keys will always be potentially faster than using tab since the arrow keys bypass any vim script while the tab key has to run through supertab and potentially one or more other plugins. That being said, I can't perceive any difference in speed on my box (arch linux, vim 7.3.177).