Finnair does not use a Tier Points system, according to Post #1862:

"Since you mentioned AY, the AA and AS flights do both credit quite nicely to them, and it's a strictly distance based program for non-AY flights, at least as for now vs. IB and BA being segment based and xx tier points per segment based on length. That may be an advantage or may not, just depends on how your segments fall into their brackets. AS: D = 200% I = 125%AA D = 250% I = 150% You need 45,000 for Gold (OW Sapphire) and 80,000 for Platinum (OW Emerald), sounds like both could be achievable based on your patterns once you see how much longer distance you'll be doing."

If you do SAN-PHX-ICT-PHX-SAN in D class, you would earn 380 Iberia Plus Elite Points, of the 2,250 needed for oneworld Sapphire, or roughly 1/6 of the way there. If you credited to Finnair, you would earn 4,696 5,870 miles of the 45,000 miles needed for oneworld Sapphire, or a little more than 1/8 of the way there.

If that trip is representative of your expected travel, then you would achieve status faster by crediting to Iberia, but you would likely amass fewer redeemable Avios with Iberia.