Some folks aren't really fond of the built-in client and there's certainly no shortage of clients available in the App Store, so please, do tell. What email client are you using on your iPad and why is it your preference?
I only sparingly use email on my iPad at all because it's wifi only and my phone almost always gets the email first, then I have to deal with multiple notifications, etc. so if I have to use email at all I use the stock email client. I did have Mailbox on at first, and I may turn email on again for the ease of emailing certain files. Mailbox is my preference for GMail though, my Yahoo's I just use the stock client.