Wait now I have a question: I have the 100k offer sitting in my offers window, too. But I was going to pass on it in favor of DH getting the CSR (I'm over 5/24 until later this year). If we currently don't have either card, is CSR the way to go? I figured yes because the travel credit is more flexible (we also don't uber much). No way DH goes for that high of an AF on two cards, so I've got to decide.
That's a hard choice.
If you're going for the CSR, are you and/or your DH under 5/24, don't currently have another "Sapphire" card, and have not received a signup bonus on a "Sapphire" card in the last 24 months? Then, if you are eligible for the CSR's 50,000 UR signup bonus, are you planning to "double dip" and also apply for the CSP on the same day to get that separate 50,000 UR bonus and get around the "one Sapphire" rule? If so, that's a combined 100,000 UR points on a $8,000 minimum spend in 3 months, which should keep you busy! Yes, the CSR carries a $450 AF, but the CSP's $95 AF is waived the first year. And as you already know, the CSR has a $300 travel credit that is very easy to use. I also find Chase's UR points much more flexible than Amex's MR points to use.
If the above makes sense to you, you may want to hold off on the Amex Platinum offer. Some people seem to regret it if they can't pull up the 100,000 MR offer again. And, if you get other Amex cards, that could decrease your chance of being targeted for high offers like 100k for the Platinum later on. However, there are tricks to pull up higher offers so there are still chances to get a 100k offer again.
Even though the Platinum comes with a $550 AF, it's offset in part by a $200 airline fee credit (note that this is much more restrictive than the CSR’s "travel" credit), $200 Uber credits (doled out $15/month with an extra $20 in December), Pre✓ or Global Entry credit, and Priority Pass and Centurion Lounge access.
Because the airline fee credit is a calendar year benefit, the best time to apply for the Platinum is in late November and December, so you have the opportunity to
triple dip that benefit (worth a total of $600) for one annual fee ($550). If you get the card in December, you can utilize that benefit in December 2018, then double dip again starting January 1, 2019, and triple dip in January 2020 before possibly canceling this card and getting a refund of your second year AF. You'd also get $35 Uber credit in December, compared to the usual $15/month, which you can use towards Uber rides as well as UberEATS food delivery.
To utilize your airline fee credit, you have to select your airline, then make qualifying charges that are eligible to be credited back. Again, this is not like CSR's travel credit, which covers very broad kinds of travel expenses. Technically, Amex will credit you for only airline fees like checked and overweight/oversize bags, change fees, seat assignment fees, in-flight amenities, etc. But a lot of people successfully use this airline fee credit to buy gift cards with certain airlines. As of last month, I know buying Southwest, AA, and Delta gift cards in certain denominations still worked to trigger the credit.
Pay close attention to recent data points on FlyerTalk and reddit for what works with what airlines. You have to be very careful doing this because it's technically not how the airline fee credit is supposed to work. Often, you have to keep your gift cards denominations small and separate, like $50 or $100 at a time; sometimes the full $200 will work (check FlyerTalk). If you don't get credited, you can't exactly call up Amex and plead, I should have received the airline fee credit for my gift card purchases (nope).
If your home airport has a Centurion Lounge and you do enough traveling to take advantage of this perk, then a Platinum card might be worth having a place to go before and after flights. We find the Centurion Lounge to be a lot nicer with better food (and alcohol) options than a lot of domestic Priority Pass lounges.
Another option might be the Amex Platinum for Ameriprise. The AF on this card is waived for the first year (and the card is supposedly very churnable). The Ameriprise Platinum comes with Uber credits, access to Centurion Lounges, and 5x MR earned on flights booked directly with airlines or Amex Travel and hotels booked with Amex Travel; but does not include the airline fee credits, GE or Pre✓, or any signup bonus. Signing up for the Ameriprise Platinum will also probably lower your chances of being targeted for a high signup bonus on the other flavors of Platinum and Amex cards.
One last thing, Amex typically reports new cards to the credit bureaus at or about the close of your second statement, so you have about 2 months from when you open a new card where Chase, for example, doesn’t see or count a new personal Amex card against you.
*raises hand pointing to myself* and DH didn't earn the nickname "plane princess" for nothing 
I wouldn't spend even that many Sky Pesos for a flight. So we booked through the UR portal instead and paid with UR points which wound up costing 374,288 UR points total. I always compare the cost of miles vs the cost of paying with points and then make a decision. I just booked my flight out to Antarctica for later this year. There were no AA saver awards so the flight out was 150,000 AA miles each. To pay for the flight with UR points on a $3,484 one way flight would be 232,267 UR points each. So I booked that with miles and the fees were less than $50 per person so that was even better.
. Ugh.
