rent increase notice, vs. new lease

[Sami Gren]

hi, i was wondering what you guys think.

i was looking around since i am about to renew leases with several of my tenants, andi am always looking for new stuff.. and  i came across 2 different types of documents, 

1) is a rent increase notice, where you let them know that the rent will increase

2) is a nice letter  that i have attached a new lease, and if they agree to the terms they should sign, (and in the new  lease i just write in the new amount......) and if not, they should let me know.

what are the pro and cons of each of them, and which  of them do you prefer to use?