Use A7 for your game prototype and make sure the models look great in a testlevel. It is easy for you to create a prototype using an engine you are familiar with.

Learning a new engine, new language, new workflow, ... for your first big project is not a good idea. If you switch to another engine, it might take up to 6 month until you know how the system works internal and what is the best way to develop a given feature.

Spend some time for tweaking the graphics and tuning the engine after you have your prototype up and running.

You should be able to export the models for use in other engines, too. Check these models in other engines and compare the visual results in terms of quality and fps.