I am trying both at the moment and like Log PI. Both have pros and cons. Log explorer has notification, indexing on search, more instance captured etc.
On the other hand Log PI has much much better GUI and easy to understand and use. It allows to filter to the row level which, log explorer is missing.
Log Explorer uses host server whereas Log PI installs its own MSDE version.
Honestly, Log Explorer is more stable but Log PI isn't far behind specially if we consider that it is only been around for little over one year.
Log PI has some new imporvements comming in next version including notificatio and faster search. If they deliver what they say then I prefer Log PI.
Best of all it costs much less then Log Explorer.
Above views are my own and should not be considered as conclusion. No offence.