The major difference in guide performance on the completed rod is as others have said, weight. The lighter the guide (titanium vs SS), the less the guides will slow down the recovery from deflection of the bare blank. You achieve the lightest guide set with choosing the smallest size you can get away with and the lightest guide in that size (titanium frame vs SS). This can be measured by checking the True Natural Frequency of the blank, then repeating it with different guides. You will see the advantage of lighter guides with higher TNF numbers. The big question is whether or not one can feel what might be a 10 % or so difference in TNF. It should result in longer casts and a crisper, cleaner, feel AND most likely better sensitivity (ability to feel a bite). Out on the rod, in the area of running guides on spin, is where the difference is the greatest. Yes, I have numbers to back up my statements. When I am after the highest performing rods, rods intended for finesse, I use the smallest titanium-framed Fuji guides (and titanium framed tiptop) I can get away with. Usually 4mm runners and tiptop.