Yes, no, maybe, no, yes, WHAT? in no specific order to the above.
Stuff you don't need to know: The U 89i is a medium diaphragm. The U 87i is an LD. Their sound differs a lot, but it's not about the size. The Schoeps CMC641 is a SD.
Other stuff you don't need to know: SD theoretically have less "scatter" when the sounds reach the smaller membrane more evenly than on a larger LD membrane. But how much is mitigated, corrupted or filtered by head grille design? Omni's are easier, but bad acoustics may forbid their use. The Gefell m296 SD mic ($1271 USD), with its nickel membrane, is absolutely stunning.
Cheaper mics are sounding better...... some yes.
The
MXL, MCA SP-1 LD, for example, now runs about $55.00 USD. When I first saw it 3-4 years ago it was only $39.95!!. In the interim, I'm told, they have swapped out the brass body for an aluminum body. Does that change the sound of the mic? it MIGHT but it might NOT. At $55, it's hard to beat. If you could get Jim Williams to put his mod on it, (don't know that he's doing that these days, but you could ask), you'd throw a few more hundred at it and definitely get something better.
I just reviewed the Aston Origin ($299 for an LD cardioid) on my blog that sounds like it should cost more. The 11 dB-A selfnoise doesn't seem to be a factor because it's .7 dB hotter than a TLM 103. Mics with less sensitivity require more mic preamp gain and that brings up their selfnoise and the preamp noise. Maybe I should do some of the review recording in my living room rather than down in the studio where the environment is a lot tighter...but not dead. That might give folks with no budget or apartment rent restrictions a better idea of how a mic performs.
There are some other interesting things going on. A few years back, Audio Technical put out the AT5040. A mic that has FOUR rectangular diaphragms. I thought, "That's nuts! How will they ever get the phase right on THAT?!?! Well, they did and it's a pretty amazing sounding mic, even in my non-acoustically-treated living room.
In the end you'll probably anguish more over finger squeaks than mic performance.
Regards,
Ty Ford