Which has lower fee's? The developer of my web applications said we should pick one of those two for easy intergration into the site...
That will depend on the reseller that you use to acquire your gateway. You'll need to shop around to see which reseller can offer you the best pricing. There are other factors to consider as well beyond pricing that may affect your business. I suggest reading Put your Money where your Mouse Is: 6 Payment Gateways Reviewed which compares Authorize.Net to Linkpoint (and others).
Hi, Yes, those are the best by far but it depends on a lot of things. If you know the volume of payments you will receive they may be willing to give you lower fees. Also, see with the bank you are working with - they may be able to assist you with this and provide you with merchant gateway through them.