if you cant hear a diff between the senn mk4 and neumann 103 you dont have very good ears, or decent preamps, or your source does not reveal the differences. Having had both these and trying them on just about everything, the senn is thin and harsh, which the uninitiated may hear as "clear" but its the same hyped high end scritchiness that most chinese mics have. Transients were smeared not accurate, also there was a weired resonance due to prob the body or capsule. Not worth the cost. not a better mic than most chinese in that price range by any means...as I believe the mk4 is chinese made...sure sounds like it. Its just a budget mic for those starting out that will sell it soon after they acquire the means and ear to move upwards.
The TLM103 is something else, and yes worth the extra whatever difference more, but ebay prices on them are very low so you can ofter get a used 103 for not much more than the new senn (ok maybe double it). The 103 is well balanced overall, has a clear high end presence that gives a bit of focus to sources that may need it, but thru a bright cheap preamp may be too much for some. On a decent preamp not harsh at all, can be silky sounding. Transients are slightly rounded, which is nice to avoid edginess. Low end is controlled...not thin or thick...just right for most sources. The mids have good detail. I dont hear any weird dips or peaks. Overall a very good useful general studio use mic very good on most anything. Is it the best on everything? no. is is a u87? no. p.s. the even cheaper
tlm102 is a smoother fatter mic, not as airy or detailed as the 103. The 102 is ok for lower end things not needing airy top...like elec guitar, etc. The senn mk4 was just useless for me. just another chinese mic. that makes the 103 worth the 700 more to me. YMMV. In your bedroom you may not be able to percieve the differences. Learning gear takes time, and money, and patience, and skill. Quik off the cuff takes often change as your skills and other gear increases. Yes its tempting to go the cheap route, but in this case there s a difference. I have had prob somewhere between 50 and 100 mics over the years so I have some perspective in comparisons.