Using more volumes is better due to the load balancing (MPIO) and the queue depth utilization. The more volumes the less queue depth per volumes.
Without any performance information I would opt to go for 8 volumes each 1TB.
Please make sure that you separate volumes for your logs, and use 4096 block size and turn OFF the caching.
For you other volumes please make sure you will use the same block size as you have defined with your db_block_size parameter in init.ora.
If you have any other questions, please do let us know