Anderson vs pella sliding door
 

I am replacing the sliding glass door out to my patio and I am trying to decide between --The anderson perma-Shield 200 series PS510 with Low-e tempered dual-pane insulating glass and---The Pella Proline series white with insulated tempered Low-E advanced glass with argon gas..

There is not a big price difference only about $350 so what I need to know is what is the best door that will last the longest and have the lowest up keep for the life of the door. I know the Pella is Aluminum exterior and the Anderson is vinyl

Best?
I think you'll find that these are both quality doors with pros & cons about both that you'll have to make a decision on.

Aluminium is better for noise if you are close to street or something.

I'd go with an Atrium door instead.
The reason why is the threshold is far stronger and I've never once been able to get a Pella or Anderson rep to come look at windows or doors my customers are having trouble with. Home Depot sells Atrium.
I also strongly suggest while the door is out you add what's called a jam sill. It will stop any water from getting in around or under the door and taking out the subfloor.
http://www.jamsill.com/
Pay special attention to the flashing under and around the door for a leak free install.
Make sure the threshold is fully supported on the outside so it can not twist and cause a leak.
A piece of 1 X 6 vinyl lumber attached with SS trim head screws works great.

only suggestion for your reference
 

maybe you have already made up your mind, personally speaking, i advice you aluminium, except the thermal performance maybe a bit weaker than PVC.
Good luck. wish you have the right one.