I've been with plain ADO connection pool, with no complains.

Why should I use DataAccess connection pool instead of ADO's?

What's the best benefit of it?

Hi Gongdo,
First of all, if you have no problems with the current settings, I would not advise to change to a different mode.
Though if you for instance have the need to fire a special init sql statement before using a connection, then you can use the 'Telerik Data Access Connection Pool' that allows you to specify such settings using the InitSql setting.
Another feature is the testing for connections, where you can say that when a connection is idle, it gets tested in the background to ensure it is valid when you request it again.

You can find more details about the different settings here.

I hope this information is helpful for you.
Feel free to ask in case you have any other question.

Regards,
Ralph Waldenmaier
Telerik