Super sprints, sprints and standard distance are proportionally more or less the same in terms of the ratio of swim:bike:run, i.e approx. 1 to 26.6 to 6.6, so assuming you maintain the same slow pace throughout there would be little difference.
When you move up to middle and long distance, the proportion of the bike and run become much longer: 1 to 47.3 to 11, so you would have more time to claw back the time on the bike and run as you put it.
I must be a pro then as I can tell the difference between my Dura ace and Ultegra!!
But don't forget, the gears/wheels/brake etc - which appear to be the main difference between the two bikes you have mentioned - can, or will have to, be replaced in the future - so you can always upgrade later on.
So as the others say, get the one that you feel most comfortable on/with.