The only consideration here is utilization. Once the card reports $0 and closed, then it is forever removed from util. That will increase your overall util if you are carrying any balances on your other CCs and could potentially decrease your FICO. Certainly that can be corrected by paying down your other cards if the balances aren't in check. For max results, pay all CCs to $0 except for one and get the remaining to report less than 9% of the CL.
FICO looks at both individual and overall util. The CLs aren't averaged in the eyes of FICO. For overall util they are added up, along with the sum of the balances and divided into that to create a percentage.
Small utilization hit &, if it's older than other cards ... maybe a hit on AAoA. I think that you are right, any loss will be recovered quickly. Congrats for closing it! They are refusing my CLI on a $300 un-secured card & it is driving me crazy. Plus, they are jerks about Goodwills. I'm thinking I'll move on from Cap One when the opportunity arrises, which should happen soon (expect the only "current" baddie, which is false, to be removed).
Good choice. Hope they don't take back the adjustment, either ... but whatever. You've got better cards, you'll eventually get most or all of your deposit back, and it's goodbye Capital One. :-)