Bandwidth and performance
PCIe tuners connect directly to the motherboard bus, providing consistent bandwidth with minimal latency. USB tuners share bandwidth with other devices on the same controller, which can cause conflicts on busy USB buses. For HD and 4K streams, PCIe generally delivers more reliable performance.
Stability and hot-swapping
PCIe cards are internally mounted and not affected by accidental knocks or cable movement. USB tuners can lose connection during movement and do not hot-swap reliably on all systems. For a permanently installed TV computer, PCIe is the more stable choice.
Number of tuners
PCIe slots are a finite resource on most motherboards, with typically two to four available. USB ports are more numerous, but sharing a controller between multiple USB tuners can cause conflicts. For systems requiring four or more simultaneous tuners, a mix of both types is common.
Portability
USB tuners excel for portable use, laptop testing, and temporary installations. A laptop with a USB tuner and a portable satellite dish is useful for field testing or demonstration. PCIe tuners are unsuitable for any situation where the computer needs to move.
Recommendation
Use PCIe for permanent desktop TV systems with one or two tuners. Use USB for portable setups, laptops, or systems that need more tuner flexibility than PCIe slots allow.