Shure SM7B vs Shure SM7dB
The SM7dB is an SM7B with a preamp inside. Capsule, sound and filters are the same; what changes is how much gain your interface has to supply.
Today the Shure SM7B costs 104€ less than the Shure SM7dB (21%).
Real deals on microphonesWhich one to choose
The SM7B is a very low-output dynamic (1.12 mV/Pa): for speech at a normal distance it needs around 60 dB of gain, and many entry-level interfaces run out or get noisy near the top of their range. The usual fix is an inline booster. The SM7dB has one built in, with +18 and +28 dB settings powered by your interface's 48 V phantom; in bypass it behaves exactly like an SM7B. If you already have a preamp with plenty of gain or a booster, the SM7B. If it is going into a basic interface and you don't want extra boxes or cables, the SM7dB: compare the price gap with what a booster costs on its own.