The “best” USB Flash Drive for you depends on what parameters that are most important to you.
Assuming you want an affordable drive with very good read performance and quite good write performance, I suggest A-Data Nobility series PD7-200x drive. It can be bought from Meritline and other places.
The drive doesn’t perform nearly as well for writes as when it first came out (labeled “Professional” instead of “Nobility”) using SLC flash instead of MLC flash, but the drive is now at the same price level as other drives that perform much worse for writes.
I have bought several of these drives.
Drawbacks: The drive cap can easily be lost since it cannot be attached to the back of the drive.
30 full CDs would hold 30 * 700 MB = 21 GB, so you can’t replace that many full CDs with just one 8 GB flash drive.