As far as we know there are no provably secure ciphers (not counting a one-time-pad with a perfectly random, secret key). So any question of security comes down to "by what measure?".
AES is well studied, but that doesn't mean it hasn't got weaknesses such as possible timing attacks. Furthermore, a block cipher cannot be used on its own, its required to use a block cipher mode of encryption. This in turn may be susceptible to attacks.
SEAL seems to be patented, which means it won't receive as much attention as AES. It has been around for some time, so presumably it's not easy to break. I found one paper that distinguishes SEAL from a perfectly random stream. I'd say that's not much, but it is probably better than any attack on the AES algorithm.
In general, after choosing a relatively well known cipher, the security of the cipher is not high on the list of possible attack vectors. No doubt that there are better ways to attack the protocol.
None-the-less, the statement that this stream cipher is more secure than AES is very dubious. And as indicated, even if it is, it doesn't matter. Stream ciphers are normally used because they're fast, not more secure.