I once spent a very amusing couple of hours in the old PA Centre in Denmark Street (before Wunjo Bass moved down there) proving to my own satisfaction that there is no practical way to 'test' how good you sound through various microphones by simply singing into them.
Ultimately, you have either have to record yourself and listen back later, or have someone whose ears you really trust in the shop with you.
I came out of the shop with a Beta 57 and used it for a year, decided the E835 suited my voice better and used that for a year, then changed my mind and started using the 57 again.
My vocal technique is very poor, and involves having my lips touching the mesh.
This is not recommended.