Which factors may affect a choice of an oviposition place in nocturnal moths?
The winter moth's preferred host plants are mainly deciduous trees, oak being the main food plant and also many fruit trees, birch and hazel. Females generally deposit eggs in bark crevices, under bark scales, bark snags and under lichen along tree trunks of host species. Eggs are initially small and green but gradually change colour to orange and then red before hatching (reference 1 and reference 2).

Though the oak is preferred, 


  There does not seem to be much discrimination in selection of host
  plant or oviposition site by the female (Wint 1983), as the choice of
  larval food plant depends on the female's pupation site and the
  direction she takes on emerging, as she just climbs up the nearest
  tree. So it might be fair to say that the larvae contribute more to
  host plant choice than the adults, as the larvae can balloon if the
  host plant is unsuitable. However there is the possibility that year
  after year each generation of females will climb up the same tree as
  their mother, and oaks (one of the most common host plants) can be
  hundreds of years old, so there could have been hundreds of
  generations of winter moth on the same tree (reference).


So that in effect means, that the thickness of branches or being indistinguishable should not be a factor. Regarding abiotic and biotic condition, the main abiotic conditions are precipitation, temperature and photoperiod. 

An increase in temperature leads to more activity and a faster metabolism (reference) Since leaf buds open faster, there is a chance for eggs to be laid faster according because the larva needs to burrow into the buds before the leaf opens (bud-burst) Hatching is temperature dependant but I do not think that it effects the number of eggs much. Biotic factors like the presence of parasitic predators reduce population but does not seem to reduce the number of eggs.. (reference)