Unless you wanted to tear down everythinng and start over (without re-using anything), why would you completely disrupt how your tank has progressed over time? I think the previous responses have been spot on, but I'll give you a few more things to contemplate.
Let's say you do as your friend suggests (give him all the plants from your tank).
1. What happens if one of you moves (relatively far away)?
2. What happens if you no longer remain on good terms?
3. What happens if your friend doens't quite have the same level of success you have achieved with the plants?
4. What if your friend loves ramshorn snails/duckweed in his tank but you think both are absolutely evil. Are you still going to want plantings?
5. What happens if your friend goes away on vacation and the unthinkable happens: 3 day power outtage, with nobody around to try and figure out how to care for the aquarium. It could take a while to recover, during which time you might not receive any plants...