Quote from: yooper on June 26, 2017, 01:32:58 AM

I've only seen 12 word pass phrases mentioned in what I've read so far, but as a noob I am less than a week into this .... new hobby I guess.

12,13,18 and 24 are used frequently, though there is no rule. It comes to implementation as to length of a passphrase. For example, Monero uses 25-word passphrase.

Quote from: yooper on June 26, 2017, 01:32:58 AM

Today I installed the coinami wallet app on an andriod phone, it created an 18 word phrase .... how significant is that? I assume if makes the crypto even stronger but maybe beyond necessity?

Technically, I can't answer to that.

Simply put, when we recover our wallet, we have to enter seed. Some(most?) wallets ask words in random order. If you have, say 24-word passphrase, over 12, then even if your words are tracked by keyloggers, they will have harder time in deriving your wallet.

Quote from: yooper on June 26, 2017, 01:32:58 AM

Also since most other wallets only use 12 words wouldn't there be a compatibility issue if you wanted to change wallets?

For compatibility, different wallets implement different seed formats. For example, Electrum uses their own seed format, Mycelium uses BIP39 and Coinomi uses BIP44. Thus, when you try to swap between clients, you need to first check seed format. You can import your whole "wallet" to another client by importing all your private keys, but it is going to be a pain in the neck.

HD wallets compatibility matrix: https://bitcointalk.org/index.php?topic=1000544.0

P.S. Do note that when you import private keys to a client, it *won't* be related to your seed unless you send your bitcoins to any of the addresses generated by your seed.