Choosing a crankset

[krashTest]

I intend to upgrade to a 11-speed internal Shimano Alfine hub along with the Alfine crankset. However, there are two different chainrings available. The 39T and 45T.

http://www.shimano.com/publish/content/global_cycle/en/us/index/products/0/alfine/product.-code-FC-S500.-type-..html

What are the determinging factors on why I would choose one over the other?

Thanks in advance.

[Painkiller]

what do you have up front now? is the rear that you are getting similar in ratio to what you are changing too? Then ask yourself what do you expect or hope to achieve with the end result.
if you live and ride in a hilly area you may want the 39t, if mostly flat and you want the top end speed then go with the 45t

[krashTest]

Thanks for the reply painkiller. I currently have a triple chainring Shimano hyperdrive. I plan to pair the new crank with a 20T rear cog, which is also a Shimano Alfine component.

Ideally it wil be used for my commute which is consists of some open street paths and mole hills in the city. It would be geared towards general all purpose riding and some light touring.

[Painkiller]

maybe there is something here that may help you decide, If unsure Iwould go with 39t. That would be somewhere in the middle of what I think a lot of people use.
http://allseasonscyclist.com/2012/07/13/shimano-alfine-11-speed-internal-geared-hub/

[krashTest]

I'm leaning towards the 39T as everything I've read has referenced it.

Thanks for the link btw, the article was an excellent read. Cheers!