I'll wager that many of the different manufacturer fiberglass whips of the equal length will be fairly comparable with each other. Maybe not in all cases, but most. I took some old Archer flexible fiberglass whips down and replaced them with a new set of Everhardt TSM antennas. After many reviews that I read, I expected an improvement. There was no discernible difference at all.
Different lengths, on the other hand, will show a very big difference. An efficiency test of a 3' Firestik showed 64% efficiency compared to a full 1/4 antenna (being a known constant at 100%). A 5' Wilson Silverload showed 92% efficient as the 102". Not that Wilson's fiberglass antenna is better than the Firestik. It is the comparison of a 3' vs. 5'. By that standard, a 4' stick would be 78% efficient. So I would go with the 5' antenna.
Most of the large, open coil antennas in the 5.5' length also showed 92% efficiency. Same as the 5' fiberglass. They were, however, more broad banded and much higher power rating. But if you are tuning only for CB and aren't running an amp, you won't need the wider bandwidth or power handling. Plus, the fiberglass whips can be bought for under $20 if you shop around.