Long rambling pre-coffee post coming up:
Which cards do you have that has you at 2/24?
What cards do you still want from Chase? Or from any other issuer in the short term that'll add to your 5/24 count?
Note that as of about 3 weeks ago, it appears all of Chase's cards now fall under the 5/24 rule.
The Chase Marriott Premier Plus and the Marriott Biz cards are subject to the 5/24 rule. The MPP will add to your 5/24 count, the Marriott Biz will not. Both the MPP and Marriott Biz offers are for 75k Marriott points after $3k MSR, with a $95 and $99 AF, respectively, not waived in the first year. Both cards come with a Free Night award certificate upon every anniversary, and I believe the FN certs on Chase's Marriott cards are posting on time for you to pocket the FN and cancel the card without paying another year's AF. However, if you pick up a Chase Marriott card, you will generally be disqualified from Amex's SPG cards for the next two years.
The Amex SPG Biz will not count against Chase's 5/24 rule, but the SPG Personal and Luxury cards will count against 5/24. All of Amex's SPG cards are offering only a 75k Marriott points after $3k MSR welcome bonus right now, unless you received a targeted mailer for the SPG Lux with a 125k Marriott points offer. As I mentioned above, a 100k Marriott points after $5k MSR offer recently ended on 10/31 for the SPG Biz and Lux. The offers will probably go back up in a few months. Note that unlike Chase, the $95 AFs on the SPG Biz and SPG Personal cards are waived (the SPG Lux's $450 AF is not waived, but you get a $300 Marriott credit with the card). However, reports are that the FN certs are posting about 6-12 weeks after the anniversary, which may not be enough time to pocket the FN cert and then canceling the card in time to avoid the AF. (So whether you go with Chase or Amex, it seems like you'll have to pay an AF to get the FN cert.)
Note that with the Marriott-SPG merger, Marriott made a lot of changes to their Chase and Amex cards over the summer so that a Chase Marriott Biz is essentially the same as the Amex SPG Biz (note the same earning structure), and the MPP is the same as the SPG Personal. Thus, Marriott wants you to choose a lane -- Chase or Amex.
Chase has 2 Marriott cards (the MPP and Marriott Biz). Amex has 3 SPG cards (the SPG Personal, SPG Biz, and SPG Lux). You can get bonuses on each of these cards, but only from one lane until the 24-month restriction passes for the other lane of cards.
At a basic level, I personally think 3 > 2. Go with Amex.
But in your situation, it's a little difficult. The Amex SPG offers aren't at their high right now. You could wait, but for how long? You'd probably be looking at the SPG Biz because that won't add to your Chase 5/24 count. The SPG Personal and Lux will add to your 5/24 count, so you might want to put these off until after you're at or over 5/24. But with you being at just 2/24, how many cards do you still want or need to get, and how soon can you get to or over 5/24 so you can break free and get the SPG Personal and Lux?
(I'll add that Amex has been flagging applicants who have a history of signing up for a card, hitting MSR and getting the bonus, then putting no or only minimal spend on those cards until it's time to cancel, and telling them with a pop up message that they're ineligible for the welcome bonus when they try to apply for more Amex cards. So if you get an Amex card, be sure to put continued spend on it.)
Complicating matters is Amex is expected to discontinue new applications for the SPG Personal in early-2019 and Chase is expected to discontinue new applications for the Marriott Biz in early-2019, as part of a deal struck earlier this year between Marriott-Amex-Chase where Chase gets the mass consumer and premium consumer portfolio of credit cards and Amex gets the super premium consumer and small business portfolio of credit cards. So unless you're in a position to get the SPG Personal or Marriott Biz (depending on the lane you've chosen) by early 2019, without throwing off your strategy, you may miss out on them.
If you choose the Chase Marriott lane, then it makes sense to get both the MPP and Marriott Biz so you can get both bonuses and eventually 2 FNs.
While the Marriott Biz won't add to 5/24, it will add to the credit lines already extended to you by Chase, which Chase uses to decide whether to approve you for more cards or if you already have sufficient (or too much) credit extended. (So keep your overall credit lines with Chase in check, ideally <50% of household income.) As a biz card, it may also affect your chances of approval for Chase's other biz cards (e.g., the Ink cards, SW Biz, United Biz). A lot of people have been approved for and have 3 open Chase biz cards with only their SSN; 4 open Chase biz cards using only SSN is tougher (but spacing out your apps and keeping credit lines low helps); and I've seen some DPs of as much as 5 Chase biz cards using only SSN. So you need to consider if the Marriott Biz is worth more than one of the Ink cards or a SW or United Biz.
As for the Marriott Premier Plus, it's a personal card so it'll take up a 5/24 slot. Are there any other Chase (or other issuers') personal cards you'd rather have? I think a popular sentiment post-Marriott merger is that the Hyatt card probably offers better value than Marriott. If you can fit both in, great! But with the MPP taking up a 5/24 slot, you need to look around to see if that slot can't be better used on another card.
