CK and Capital One's tool are much more sensitive to changes, from what I've seen.
As far as Discover and Amex, both are good banks that do offer chances to grow quickly. Look at the benefits you like of each card to figure out what you want to go for in the future. Neither would be a bad choice
State Farm Rewards (3,000) ~ Marvel MC (8,000) ~ PenFed Power Cash (5,000) ~ PenFed Promise (6,000) ~ PenFed OLOC (500) ~ Discover ($1,000) ~ Citi DC (1,700) ~ NFCU cashRewards (6,200) ~ NFCU Platinum (1,700) ~ NFCU CLOC (15,000) ~ QuickSilver Visa (10,300) ~ DCU Visa (5,000) ~ Chase Freedom Unlimited (3,000) ~ Amex Hilton Honors (5,000) ~ Amex SPG Business (3,000) ~ Care Credit (15,000) Current Scores (7/8/17): 682 Transunion, 648 Equifax, 673 Experian