Matter of taste. All witcher armors of the same class have nearly identical values. The most changes to them will be done by adding runes in many different ways (not counting the rune smith from HoS).

The most they differ is related to the possible taste of the player (magic orientated vs. sword orientated): so for a tank I would use the ursine type, for a more magical approach I would use Ofiery epuipment, and after I have seen that witcher equipment has not the highest values by far - I simply would not use any at all (if it were not for the treasure hunts).

With all the rest of the junk you can assemble in W3 I believe there is more then enough to chose from, both concerning value and appearence.

I too was surprised by the fact that the Manticore set is not considered light armor, but remember that the Runewright can provide you with an effect that (when applied to the chest piece) will make it so all equipped armor is treated as Light, Medium or Heavy, allowing you to take advantage of the pertinent skills in the general abilities section. It's not an ideal solution, because he's only available through the Hearts of Stone expansion, so it may prove inconvenient to some.