I have quite a few 12AU7 types which also include the 5814A variation. The better Euro stuff IMHO was the Telefunken and Mullard types (marked as ECC82)... both excellent but most seem to prefer the smooth plate versions of the Telefunken. Many of the later Amperex 12AU7 and 12AX7 has really smallish plates in larger diameter glass... never really cared for them. The older Bugle Boys were really nice.
In the US, you have many to choose from, Sylvania (later ECG-philips), RCA, GE, Tung-Sol... Heinz Kaufman and others. I have sourced numerous NOS ECG-philips JAN 5814A tubes and they are excellent. I also have many RCA black plate 5814A tubes and some GEs as well, but I prefer the RCA over the GE, and as already noted, RCA cleartops (named as their getter is attached to one plate on the side). RCA also had the Command series which was a more rugged and better spec tube intended for broadcast use. GE had their 5-star series which was the same. The broadcast series usually had triple mica spacers... and better microphonic specs.
In general, I tend to prefer the sound of Telefunkens in preamps, second to Mullard. They do very well in a properly designed unit and low-level signals. For power amp usage (my 45 and 2A3 SET designs use a 5814A) I prefer either the RCA Black Plate or JAN ECG-philips. Both are very open and neutral... the Mullards sounded a bit muted actually.
Regards, KM