If you're going to use 603's on a loud drummer, you will need to pad the signal. Hopefully your mixer has one, or you have some inline.
I've never tried the Octava products so can't comment. As for self-noise. Well, the 603's are quiet when they are working properly. When they are not you will get some random spiking and hisss out of them.
I've found this to be an annoying trait with the MXL products I've used so far (no more).
I have two 603's. One is prone to go into low level (-39) 'hiss/seashore' 'spike' mode at random. The v67G I have does a similiar thing. No it isn't my mixer or pre's or a phantom power problem.
When they work, they work well. But I don't put a lot of trust in them.
I went through three V67G's before I found one that didn't either have the surf-surge problems, grounding problems or a combination of spiking and ocean sound effects. The third one I kept, it is prone to this. I can work around it, but like I said, I don't put much trust in it.
I've sent back one 603 to MXL in CA for repair. It came back and worked for awhile, and then went into random spike/hisshh mode.
I don't have many other condenser mics. A rode NT-1, three AKG C1000's. None of these cause me problems.
I usually end up using my trusty 12 year old C1000's if recording someone other than myself, just to avoid the intermittent performance, and unavoidable resultant grief.
Maybe I've just had bad luck, whatever the case. Three defective V67's, Two defective 603's doesn't inspire much confidence in me purchasing further MXL products.
QA indeed.
Given the choice, I'd try the Oktava.
If money is not an object, look into AKG's/Neumann/Shure's/AT's offerings.