Yes, using 4 player trick can improve your spw (score per wave), but that
comes at a cost... one of them being that you only have 1 player bombing
so you get overall less score. but if your goal is to gain as much score
as possible, then this is by far the best current way to do this. On the
other hand... you need a stronger base because you only have 1 player
bombing and you also need to upgrade the base a lot more (mostly bombs) so
that you don't have a bunch of overlap. Most people would think that using
4 player trick would get you 4x the score because 4x the zombies... but to
those of you that think that, you'd be wrong. But why? Well with 4 player
trick the alts don't leave until after the zombies spawn, so during this
time some of the zombies get killed and the score gets split into the
alts.. this causes you to lose about 3-5m per wave in total, then you have
the towers upgraded more to prevent overlap, well this also increases the
chances of your base stealing kills, which gives you less score than if
you or your pet killed the zombie. But lastly, and possibly the biggest
reason why you don't get 4x the score is that, you only have 1 player
bombing and 1 pet, so you and your pet will kill less zombies and the base
will kill more, resulting in less score per zombie kill. So in the end you
only get about 2-2.5x more score by using the 4 player trick.