Is there a reason to choose J1900 over newer models like J3455?

Comparing this board: www.newegg.com/Product/Product.aspx?Item=N82E16813157497
to this board: www.newegg.com/Product/Product.aspx?Item...13-157-727-_-Product

Seems the newer/faster board is slightly cheaper (not that it matters so much). But looking through some threads here and reading about preept-RT requiring more CPU, makes me think the faster model would be a better idea. But are there any gotcha's to look out for?

Lastly, I have a case and power supply from a Gateway SX2110G-UW318 where the mobo died suddenly. This case will take a m-ITX but won't quite fit a m-ATX (has 2 PCI-e slots instead of 3). But I still have a 4G ram card from the original mobo. It's a full size dimm and I can't find any m-ITX mobos that don't take so-dimm. If I can't reuse it then, I can't reuse it. But wondering if anyone has any suggestions.

btw, I'd like to have both parallel port and Mesa options (probably end up with the 7i76e eventually).

Thanks,

I have a J3355 and its nice except it had troubles with older dists like Wheezy so it may not
be the best host for a RTAI/Parallel port configuration