If you fly with a companion at least once a year, Platinum or Reserve are a much better option than the Gold since the AF is more than paid for that way. If you have or want elite status and can do a fairly significant amount of spending each year ($25k or $30k increments), Platinum and Reserve are generally going to be better options than the Gold. If you want upgrades, Reserve is almost a must. If you want to do Pay With Miles, you will need Platinum or Reserve.
Gold can be a good entry to see if SkyMiles cards make sense though, and as long as you and/or up to 8 companions would pay for baggage fees on at least 4 bags a year, it's not a loss. There are usually upgrade offers later on after a year if you would prefer not to have another new account (although you would miss out on higher new card Welcome Offers) and the fee is almost always waived the first year for Gold.
@Anonymous wrote:One question, tangentially related but possibly helpful in deciding whether the platinum is the better option. I think I know the answer to this (thinking it's a No), but I've never come across it being explicitly answered. With the annual companion passes: when one receives it on the anniversary, if it isn't used in the next year, is it kept and another granted on the next anniversary? Or is it forfeit and "replaced" by a new certificate? I've wondered this in the past and never got around to asking. It'd be great if they weren't expiring, and a cardmember could save a few of them over the course of a few years to use together, but I'm assuming that's not how it works.
The certificates typically expire one year from issue. Due to the pandemic, they keep getting extended though. I currently have six of them in my SkyMiles account from 2019 and 2020 renewals on 3 cards and they all currently expire 30 June 2022. From my understanding, any new ones issued in 2021 will be valid through 31 December 2022.
@notmyrealname23 two quick things I wanted to address.
While Delta does not have an award chart, main cabin award fares are at worst essentially tied to revenue prices and would yield a minimum value of 1.2 cents per mile. Paid upgrades to Comfort+, Premium, First, and Delta One seem to be pegged at 1.15 cents per mile. For PWM, they are 1 cent if redeemed in 5k blocks (it's 5000 per $50, so $201 would require 25k, and it's better to use 20k to cover $200 and pay the $1 out of pocket so you don't waste 5k SkyMiles on $1 in this example). PWM really only makes sense if you need MQMs, although for 2021 award fares are earning MQMs and MQDs (a first for a US carrier). But with frequent award fare sales, you can do much better than 1.2 cents.
As for hyper-expensive tickets needed for companion fares, it's actually the exact opposite. All L, U, X, T and V fares are eligible for the companion tickets - those are the discounted cheap main cabin fares. It's actually the expensive last-minute tickets (like full fare Y) that are excluded from companion fares. Similarly for the Delta Reserve pass, it includes those, the C+ W fares, and the cheaper First Class tickets (not full fare J and F fares).