Your observations are correct.
The RadDropDownList was indeed intended to target the cases where you need the simple functionality of the ComboBox, while keeping the overhead to a minimum. Most of this is explained in the following blog post:
In terms of performance and reduced overhead we targeted the following fields:
- The size of the stylesheets
- The page size
We also have included a better keyboard support (with handling for the PageUp/Down keys for instance), and a new feature called VirtualScrolling (replacing LoadOnDemand), which makes the faster when dealing with large sets of data (with both server and client binding).
The reduced size of the .js and .css files is obvious - less than 50% (not counting the common scripts which are loaded for every control, like Core.js etc.). As for the page size, we examined it further and came to the conclusion that we can improve it so that the item doesn't include the additional "span class=rddlItemText" element unless an ImageUrl is set. This will be fixed for the official 2013Q1 release.
We also investigated the ViewState size of both controls in different settings. Our tests show that the amount of ViewState depends on the way you bind the control. With declarative binding to an ASP.NET SqlDataSource we also registered a 10% improvement. However in other binding scenarios(like binding to a list from CodeBehind) the amount of ViewState dropped by 40-50%. We will however look further into this and do our best to reduce the ViewState even further.
For your feedback and involvement I've updated your Telerik points.
the Telerik team
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