Articuno vs Lapras

First off, Articuno can't defend but honestly there's no such thing as defense anymore so that really doesn't matter.

I would give Articuno a slight nod on offense but playstyle is a factor.

Attack: Lapras. For raw DPS output, Articuno.
Defence: Lapras, because Articuno can't defend.

Lapras is really good in both attack and defense. Water/ice typing is synergistic. Lapras also has low def stat. This will make him gain energy faster per HP lost.

Might depend a little what you are attacking. For example, if you attacking something with fire or steel moves, such as Dragonite with Steel Wing, then Lapras's water type will offset the weakness.

Depends on whether you use them for gym battles or raids... If raids, I personally prefer Lapras due to its high stamina and staying alive long enough to outdps Articuno. For gym battles, I have yet to use Articuno against Dragonites, so I can't give out any conclusions yet. Maybe Lapras too but it might be because I have get used to using Lapras against Dragonites that I am favoring Lapras over Articuno.. I will use Articuno from time to time because looking at the same Pokemon and battling animation is boring.. Lol