This web site describes how to shop for the correct cage for finches.
http://www.robirda.com/flight.html
I always try to buy a cage that is longer than it is tall since finches prefer to fly horizontally rather than vertically. If you buy a tall cage you end up with a lot of unused space in the lower half of the cage.
Re: the two web sites you posted.....I think both sites belong to the same company. Personally, I wouldn't buy from them since I prefer to know where a company is located and where the cage is being shipped from. I also like to have a phone number so that I can contact them directly for customer service. I choose to pass over any site that has email as the only 'contact'.
I'm curious as to why you have birdscomfort.com listed as your website in your profile?
If you're interested in having a custom cage made, powdercoated either white or black, contact
www.qualitycage.com. Their prices are very reasonable.