Ex "db" or Ex "db eb" 1

Better for what, specifically?

Ex "db" is flameproof construction (d) with level of protection "b" (high).
Basic design is strong enough to withstand internal explosion; flame path long enough to prevent ignition of external medium. Design allows internal ignition sources (like hot spots and sparks).

Ex "eb" is increased safety (e) with level of protection "b" (high).
Basic design is an increased safety level for normally non-sparking equipment. Design does NOT allow any unprotected sparking components inside.

In terms of enclosure construction and rating, the "db" criteria is generally more stringent, because it has to withstand an event created by the internal spark. The "db" design will tend to have better fits (component to component) and "custom" seals between moving and stationary parts in an effort to eliminate flame propagation from the internal volume to the surrounding external medium.

My guess - and it's only a guess, since I don't always deal with IEC ratings - is that the "db eb" rating means flameproof without having an internal spark capability. To me, that would seem to indicate that the "db eb" is likely a safer way to go.

Converting energy to motion for more than half a century

The following states a summary of some potential benefits:

This provides a very cost-effective solution that facilitates easy maintenance, allows cables with lugs to be easily handled and cable terminals to be easily accessed.

Ex:

SIMOTICS XP MOTORS
Ex db eb IIB/IIC
Main terminal box concept

Is this not the Exd Exde situation where a motor might be Exd but the associated terminal box is Exe. An Exd motor with an Exe terminal box would be Exde.
An Exd enclosure is certified specifying size, power within etc and this is difficult to do with the terminal enclosure hence the hybrid.