Currently, there's generally no better option than the merchant's cloak, for most purposes.
Having the additional inventory line is huge.
As soon as one has one, one tends not to bother with other cloaks.
I happily continue to wear my plain capes, but plain tabards, unless briefly for aesthetics, are useless.
There's little reason to wear other cloaks in many circumstances, it has a buff that can't be matched.
Most other items can have their qualities be matched or similar.
I'd request that the merchant's cloak buff either be added to other cloaks, added to a gild of somekind, or, failing that, as evil as it is to say, changing the buff to an extra pocket or three might also work.