First ask yourself how often you use the 28T back there.

If all the time, then you may enjoy the 34T to climb over tree trunks and boulders. The downside is that you may not find the right for the others, like gear#4 minght be too easy yet gear #5 too hard to use.

If barely or never, then stick wth the 14-28T as these are all-condition sprokets.

For example, most of my cycling is urban commuting, I usually have 12-23T or 12-26T in the back.