Preferred pmp's with fixed rates are my favorite tbh because I'm not forced into trusting publishers with frequency capping and even pacing like with PG deals.

Id recommend you ask your pubs about the waterfalling of their inventory and the priority tier that pmp vs. Pg deals get.

Lastly looking at the price differences could help decide. A 400k budget for a 9 month flight spread across 4 pubs shouldn't have trouble spending, but it depends on your potential campaign restrictions+parameters.

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For a PG deals no additional targeting / filtering / frequency/day part / etc can happen through the DSP, it must all be applied to the deal More on reddit.com

In terms of actual fees, the cost of ad serving is the same regardless of whether the impressions are delivered via direct/sponsorship, PMP/PG/PD, or exchange. Our direct campaigns have a higher rate because of the labor costs and access to inventory/1P not available via PMP or exchange. Our PMP rates are roughly 2x exchange CPMs but much lower than direct rates. We believe the significant reduction/elimination of fraud and access to 1P warrant the higher rate over exchange. I don’t leave much wiggle room to negotiate PMP/PG rates as they’re already heavily discounted, but there’s always some room to reduce if the scale/budget is high enough. More on reddit.com

I was a buyer for many years and if someone sent me an invite to a PMP deal I would ignore it, 100%. Your job is not easy, big agencies usually have signed deals already with their preferred partners and those include certain spend thresholds that have to be met so a programmatic buy will be reluctant to try something new and unproven that also takes budget away from his priority pubs. Your best bet is to go directly to the account teams and not the programmatic buyers- unless they are one and the same but this is rare for big agencies. The account team generally knows less and is more easily swayed to try something new and will compel the prog team to run it. (unless the prog team has had a bad experience with this pub, they usually won't push back too much). You can try going directly to the client, but that can backfire if the account and prog team get the impression you are trying to circumvent them. Again, your job is not easy and I ignored 99% of calls, emails, etc... I got from new pubs. There just wasn't a lot of time to go around to meet with every solicitation. More on reddit.com