I fly out of SEA as well. For me the different between Silver and Gold/Plat is virtually assured upgrades on my second sectors, e.g. MSP/DTW to destination.

Upgrades out of SEA are extremely difficult since they cut the lift out of here a few years ago and inflated the Gold/Plat ranks with 2XEQM, etc... I'm about 50% this year to/from SEA, even as Plat. I have been denied on full 757s when buying expensive H fares a few days before flying.

My second segments, beyond the hubs, tend to be hops to MCI, ORD, etc., and while the upgrades and free drinks are nice to have, they're short flights and there's no food. I would invest in MR to improve my elite ranking if I thought it would result in more upgrades to/from SEA, but as I'm only hitting about half the time as Plat, I don't think the investment for me is really worth it.