Lockinfo all day! You can read either a portion of an email inside your notification center (depending on the number of lines you choose in lockinfo settings) or you can tap on an email and read the entire thing inside notification center. In fact, you can mark every notification line item in notification center as read, delete items, instant clear an entire section, and it has collapsible sections.
So yes, from the notification center you can mark the email (or any other notification) as read. Plus, lockinfo has status bar icons for everything...emails, texts, notifications, missed calls, voicemails etc. You can access your notification center from the lockscreen too and you can use lockinfo's HomeScreen festure and implement any notification center addon as a springboard widget. I use the Calendar Widget Pro NC Addon as a calendar widget on the first page of my springboard with two rows of icons plus my dock underneath the calendar. Last but not least, it's extremely customizable and theme-able. I highly recommend lockinfo.