Tourist visa renewal?

The immigration agents have wide freedom, so, it is not predictable. If you have bad luck and the agent is nationalist, then you are in troubled after the ARA San Juan u boat disappeared after it had an issue with a British u-boat.
The best is to arrive to Argentina from Uruguay because if you get rejected they just send you back to Uruguay and they do not have a jail for foreigners there.
Come from Uruguay by bus NOT by boat.
Out of interest, why is it better to come by bus rather than take the boat? And also should I do this even when I first come to Argentina? Or just when I am returning from holidays in Brazil, Mexico etc?