Replacement PC: Optiplex SFF vs Mini-Tower and i7 vs i5?

[Post]

My old Dell XPS (i7-4770, 8gb) dedicated to Blue Iris crapped out. It did a good job but I'd like to get a cheap used Optiplex as a replacement. I have 16 -3MP Swann (Hikvision) cameras and record 24/7. I run Win10 and Blue Iris on an SSD, and record on a 4GB Purple hard drive. I'd like to install the old drives on the new machine. Two questions:

1) I'd prefer the Small Form Factor (SFF) over a Mini-Tower but concerned about possible overheating. What do you all think about the SFF cases given that BI is recording 24/7?

2) Recommendations between these two processors: i7-4th gen vs i5-6th gen? Or, would you spend another $100 or so for an i7-6th gen?

Thanks for any input!

 

[LopezEL]

I think only 5th Gen supports h265 hardware acceleration. I'd go 5th Gen or higher just for that reason.

 

[fenderman]

You can find i5-8500 systems for about 300..they are more powerful than 6/7th gen i7's