Either here or elsewhere (I think here) I posted a list of the senior US officers at around that time (based on an early ACW thread). Scott is certain to be the Field Army Commander, and he is truly excellent, IMHO better than Lee (but not Longstreet, IMHO the best field commander of their side).
The main difference between Longstreet and Lee is that Lee had 12 more years of experience outside West Point (Lee 1829, Longstreet 1842)
IMHO, the Confederacy had more of the higher-caliber generals (Lee, Longstreet, Stuart, Jackson, Johnston, Beauregard). Their main problem was lack of industry and lack of manpower.