A ruling from 2004 says that Spike Weaver would enter with 4 +1/+1 counters after resolving Otherworldly Journey on it. However, this seems to be in direct contradiction to 616.1:

If two or more replacement and/or prevention effects are attempting to modify the way an event affects an object or player, the affected object’s controller (or its owner if it has no controller) or the affected player chooses one to apply, following the steps listed below. If two or more players have to make these choices at the same time, choices are made in APNAP order (see rule 101.4).

Can we get an Official answer on this? 616.1 doesn't list the ruling from 2004 as an exception to its possibilities.

The ruling is correct. A Spike Weaver returning from an Otherworldly Journey will enter the battlefield with four +1/+1 counters on it.

An effect that says an object enters the battlefield with counters on it is an instruction to place that many counters on it as part of the action of putting it onto the battlefield. Multiple effects causing an object to each enter the battlefield with some number of +1/+1 counters on it are not mutually exclusive, for the same reason reanimating a Spike Weaver with Makeshift Mannequin doesn't make you choose between either three +1/+1 counters or a mannequin counter. All of the relevant effects apply, and you get all of those counters.