At the end of a class on ברכת אבות Avot blessing at the beginning of the amida someone mentioned that I hadn't dealt with the גואל/גאולה redeemer/redemption issue and I responded that indeed I hadn't, because I wasn't sure what to say about it. Since then I have thought about it a lot.
I grew up saying גאולה/redemption and was actively taught that Jews “believe in the messianic age not in the Messiah.” This was largely an anti-Christian polemic and considering the rather evangelical environment, made a lot of sense.
When I started using more traditional liturgy, the transition to גואל/redeemer was not difficult, based on the idea that real change in society is usually led by galvanizing figure who can focus the energy. Therefore, I'm not sure that there's much difference between גואל/redeemer and גאולה/redemption, since the גואל/redeemer is simply the instrument that brings גאולה/redemption.
On the other hand, as I mentioned in class מביא גואל /brings a redeemer that is different from other places in the liturgy where God is called גואל ישראל /Redeemer of Israel and in the other divine attributes and actions in the list, in which God is seen as the active force healing the sick, freeing captives etc. Perhaps the form מביא גואל /brings a redeemer comes as an example that reflects on the other actions we attribute to God; just as we attribute to God redemption that is actually realized through human agency, we need to understand that the healing and other desired ends attributed to God in the preceding list are also achieved through human agency.