Entry level often means either there are variants of the same model, and this is the least expensive variant (much like automobile trim levels), or there's a newer variant and the entry level was the best to be had two or more years ago. ;)
Cost is usually the most noticeable difference, since the entry level model has either less performance and/or less features. However, the cost is not always directly related to proportional performance even if features are the same.
Don't get hung up with marketing speak, but carefully compare datasheets to your needs. If we return to my analogy of automobiles, an entry model might not have A/C but the deluxe version does. Importance of this particular distinction, to you, might be whether you live in Florida or Alaska. Likewise, how you might use a 4500 might be more important than whether it's entry level or not.
