It's a little while since you posted the above, but I see no one else has responded, so I'll give you some comments.
If you choose the 896, you'll then require a separate MIDI interface, whereas, as you say the 828mk2 already provides this.
Having used both the 896 and the 828mk2, I would say that the quality of the converters at 44.1kHz or 88.2kHz is very similar if not identical - and both are better than their prices might suggest, so good value.
As I see it, the key differences are:
1. The 828mk2 provides MIDI I/O which is not available on the 896HD.
2. There are six more built-in Mic preamps on the 896HD.
3. More/better metering and easier access to some front anel options on the 896HD.
4. The 896HD gives super-high resolution options (up to 192kHz) whereas the 828mk2 stops at 96kHz.
5. All XLR and XLR/TRS combo connectors on the 896HD, whereas the inputs are mostly TRS on the 828mk2
6. The 828mk2 actually offers more inputs than the 896HD (20 as opposed to 18) because its two on-board mic pre inputs are additional to the 8 standard line-level inputs (whereas on the 896HD they are integrated as part of the 8 channels).
7. The 896HD is bulkier (2RU as opposed to 1RU).
8. 828mk2 provides S/PDIF in/out connections instead of the AES/EBU in/out (XLR) on the 896HD.
9. The 828mk2 provides SMPTE I/O which is not available on the 896HD.
So although they have some features in common, there are a number of things that each provides that the other does not. That being the case, it is likely that one will be a significantly better fit for you than the other. [Edited as per comments from tINY below]