QlikView Expressor (QVE) supports native connectivity using high performance ODBC drivers. ODBC being specially designed to access SQL data - where as the OLEDB API can access any type of data in a COM environment.(Component Object Model).
In regards to performance, that is actually a common misconception about OLEDB being faster - I have had the opposite experience where ODBC has been much faster. - There are pros and cons of each implementation - that you can scour the Internet over and find information that will lean in both directions.
Expressor prior to the acquisition has been known for its ability to access and load data fairly quickly. High Speed performance has been one of the differentiators. With the introduction of its patented parallel partitioning (spawning multiple threads within multiple processes ) - we have been able to achieve linear performance when loading data and adding more hardware in a scale-up model.
Your results will vary of course - the best option for you is to test it yourself within your configuration and note the results.
More information can be found at the link below in our documentation in regards to the data connectivity QVE provides.
If you have any concerns or additional questions about this and require more comfort in this regards please reply to this post and I will address appropriately.