Why do we say Hamotzi?

The gemara on daf 38a says that it's a machlokes between R' Nechemia and Rabonnon what bracha to make on bread. They both agree that it's ok to say motzi but only the Rabonnon say you can say hamotzi. Yet the gemara concludes that you should say hamotzi. Why?

1. Tosafos answers (quoting the Yerushalmi) that the advantage of hamotzi is to break up the mems. This way the lechem min won't run into each other because there is the hay in between. Tosafos then asks another what about lechem min. Why don't we do something there. He answers because it's a pasuk. I was thinking that even if you say lechemm in, people will know what you mean. It doesn't mean anything that way so it's obvious that it means lechem min. However if you say haolamm otzi. It will sound like you are saying "I will take break out from the ground" so it has a different meaning. Therefore Chazal was much more concerned about that.
2. The Ritva says (quoting the Reah) that the gemara doesn't mean that you have to say hamotzi. It just means that you can say either or and he therefore concludes that you are yotze if you say motzi (this doesn't really answer why the minhag is to say hamotzi l'chatchila).
3. The Ritva says (the answer he likes) that hamotzi is better because it implies past, present and future and grain is always coming out so this way we allude to that fact in the bracha. Motzi though does not imply future. He says that this is why we don't say Haborei pri haeitz - because fruit are seasonal not like grain and vegetables. He says haadama isn't Haborei just to be consistent. My only problem with this explanation is that the gemara seems to go out of its way to show that the Chachamim understand hamotzi to only be future and not past.

There are actually a lot of other explanations. I saw the Tzlach this morning but don't remember it well enough to write it up. Also I just googled and saw some other explanations. You can see Rav Kook's explanation here. Feel free to post other answers in the comments.