Need my 27 yr old gray flex duct replaced. Have two quotes. Would like some advice on which company to use.

Small company - came recommended from a friend, didn't leave a paper copy of the quote, quoted R6, very good price. Not leaving a quote and quoting R6 raises some red flags for me. Am I just being too critical? I do like the price.

Large company - left detailed paper copy quote, R8, want to move return registers to top of walls, cost is double the smaller company. Like the detail of the large company but do the returns registers need to be moved? Overkill? The HVAC system has worked good for the 10 yrs I've been in the house. The bills are not too high. 2000 sq ft house.