Definitely 1/48th scale; I love the detail on a Carousel 1 or my 'lone' Marushin!!
Franklin Mint puts out an enormous variety of quarter scale and SOME of them are very good. Now Hobby Master is joining the fray so I think this scale will become even more popular. I have about 35 1/48th scale aircraft to mix with my 80 or so 1/72nd aircraft. If you work at this, you can cram different scales on one shelf, mixing aircraft on stands with those on their landing gear. I counted 28 aircraft on a 3' by 3' shelf and there is 2 1/32nd scale and 5 1/48th on this shelf as well!!
For armor, I prefer 1/32nd scale; tanks and other armored vehicles are supposed to show strength and invulnerability; I do own 45 1/72nd scale tanks, but I have an excellent mix of 1/32nd and 1/50th scales as well. Also, the larger scale tanks usually have crewmen with them and there is more detail on them than what you can do with a 'toy-like' tank in 1/72nd scale.