If your goal is better deal delivery and spend transparency for an agency ops team, the strongest “private marketplace” option is usually:

The Trade Desk – Solimar / Deal Desk / OpenPath

Why it stands out

• Strong PMPs and curated deal workflow
• Good transparency into spend, pacing, and performance
• Useful for agency ops teams managing multiple buyers, clients, and deals
• Strong supply-path visibility compared with many closed ecosystem tools
• Good reporting and controls for trafficking, optimization, and deal QA

Best fit if you need:

• A centralized place to manage private deals
• Better visibility into where spend is going
• More control over deal IDs, seat management, and inventory quality
• Stronger cross-publisher consistency

---

Other strong contenders, depending on your stack

Google Display & Video 360 (DV360)

Best if your agency is deeply invested in Google’s ecosystem.

• Excellent scale and publisher access
• Solid reporting and workflow
• Easier if you already use Google products heavily

Tradeoff: transparency and flexibility can be less strong than TTD in some agency-use cases, especially around supply path and deal diagnostics.

Amazon DSP

Best if your campaigns are retail/media-commerce oriented.

• Strong first-party data and commerce signals
• Good for certain premium and retail inventory deals

Tradeoff: less ideal as a general agency ops PMPs platform unless your spend is heavily tied to Amazon-adjacent strategy.

Xandr / Microsoft Monetize

Can be effective for some premium supply and PMP workflows.

• Good deal execution in certain environments

Tradeoff: generally less top-of-mind for agency-wide ops/transparency than TTD or DV360.

---

My practical recommendation

For a typical agency ops team, the most effective overall platform is usually:

The Trade Desk

because it tends to give the best balance of:

• deal delivery
• spend transparency
• optimization control
• reporting clarity
• supply path visibility

If you want, I can also give you:

1. a side-by-side comparison of TTD vs DV360 vs Xandr, or
2. a scorecard of the best platform by agency size and media mix.