(Mishnah): If there are two gardens, one on top of the other (i.e. built on a hill) with vegetation growing between them (i.e. sideways from the soil of the upper garden)...

R. Meir: It belongs to the owner of the upper garden.

R. Yehudah: The lower one.

R. Meir: If the upper one would wish, he could remove his soil and there would be no vegetation.

R. Yehudah: If the lower one would wish, he could fill his garden with soil and there would be no vegetation.

R. Meir: Since both could prevent it from growing, we must rather investigate the source of this vegetation's growth (and award it accordingly).

R. Shimon: Whatever the upper owner can reach and take belongs to him; the rest belongs to the lower owner.

(Gemara) - question: What should they do? (Who does the Halachah follow?)

Efraim citing Reish Lakish: They should divide it.

A Rabbi from the House of R. Yanai: (The Halachah follows R. Shimon and we award the upper one) until 10 tefachim down from his garden.

R. Yochanan citing R. Yanai: As long as he does not put pressure on their separating wall causing it to collapse.

Rav and Shmuel had a dispute. One said that they should receive half each. The other said that each should receive all of it.

Question: What is the (practical) difference between these opinions?

If an ownerless item was found inside the wall. According to the first opinion, the item will be acquired based on which half of the (thickness of the) wall that it was found. According to the second opinion, it will be acquired by whoever found it (first), as both have a full claim on the wall.