Yeah, definitely use Sikaflex for the sealing job (but I can't recall which type of sikaflex from memory....there is a specific compound recommended though).
As for which is better.....which one do YOU prefer.
If you are interested in a cyclonic precleaner for extreme dusty environments, then a Safari is realistically your only choice - due to the design of the snorkel head, the safari snorkel body is the only one that can take a cyclonic pre cleaner. People don't use them much these days, but with the tiny little rectagular paper filters on vehicles like the Navara, I would have thought cyclonic precleaners would be more popular than they are for outback/remote area travel. But apart from that, whichever one you like the look of best, or whichever one you can get the best deal on.
What is of PRIMARY importance is the quality of the installation...as I alluded to in my previous post. No point in having a snorkel if it isn't sealed properly (unless of course you just got it installed for looks only).