I would avoid both vehicles.  For the Suburban, if we are talking about the 1500 then it had up to 3 engine options, 2 of them being the Vortec 5300 5.3 L V8 (either LY5 or LMG engine) and the 3rd being the Vortec 6000 6.0L V8 (L76).  All 3 had cylinder deactivation which GM calls AFM (or active fuel management).  Those were the early years of implementation for AFM (started in production around 2005) and overtime those can wear out/damage the engine.  You can disable via software but the hardware (cam, lifters, oil manifold assembly, etc.) are all intact and can still fail.  GM never really got them to work flawlessly even over a decade later.  Then regarding the 2008 Ford Expedition, the only engine was the 5.4L 3V Triton V8 which was very problematic and could cost you a new engine ($6,000 or so).

I wouldn't recommend either but I honestly I think the Chevy is a tad bit less problematic.