Welcome! Both machines are noisy.
Out of those two options, I would go for the EM6910.
Ive used a EM5900 before and think its quite painful to use (especially the wait time and the purging that needs to be done when you go from espresso to steaming).
The EM6910 is easier to use but is a loud machine also. The great thing about these machines is that you can extract your coffee and then steam your milk at the same time.
If you were to pick from these two machines, then I would go for the second one. Just make sure you follow maintainence procedures...
Keep your eye out on the coffeesnobs for sale thread :)