String theory is very ambitious and tries to explain alot with one underlying idea, meanwhile LQG is only a quantum theory of gravity.
The main problem with LQG which is not apparent in string theory is that it violates
Lorentz invariance. This causes quite a few problems with special relativity by selecting a kind of 'prefered' reference frame. This is not allowed in the theory of SR.
String theory was not really in the spotlight until 1984, when super-symmetry was incorporated and as a result it becoming a candidate for the 'theory of everything'. The unifying theory, that brings together all 4 forces into a nice, neat, nicely packaged set.
LQG cannot even dream of this
It is only (at the moment) a theory for gravity and cannot be extended to incorporate other forces under the same 'framework'.
To address the 'more reliable' bit, ST has derived the
Backenstien Hawking formula for black hole entropy for extremal black holes. LQG
apparently has but has to assume an artificial value for the
Barbero-Immirzi parameter.
As a result string theory has become the preferred theory on quantum gravity AFAIK.
This is probably why you dont see much on it xD