I have worked in fitness equipment retail for 8 years now and have a Bachelor of Physical Education. To answer your question, it does not matter which peice of equipment you use as long as you're comfortable on it as all cardio equipment is mean't for weight loss or cardiovascular excercise. Ellipticals are good because they are low to no impact while still providing weight bearing activity to keep the bones strong. Problem with ellipticals is that you need to be able to put forth $2500 or more to get one that feels good, is biomechanically correct and can handle your "bigger" stature as you'll want something well built. Recumbent bikes are much cheaper, will provide you with cardio/weight loss excercise and are easy to use. Ellipticals are more efficient than the bikes because you use your entire body meaning more calories expended over a shorter period of time. People also tend to get bored on the bikes. My suggestion is to go to a gym and try them both before you buy. Last thing you want is to buy something that you don't like. As for a website, I am unsure of that. Try some of the fitness equipment manufacturing sites such as many times they will have helpful hints on buying the equipment. http://www.precor.com, http://www.iamstrong.ca (this one is more towards health and lifestyle and has testiomonials).
Hope this helps!