Well there is a relevance of chips <-> device coz it affects the difficulty.
The J'things produce a lot less GH/s per chip.
If that impacts the overall hashrate by more than 10% I'd be amazed. Many more chips will be going into the other models, which means that the slower speed of the Jally should be discounted to 25%, 12.5% or less on a per unit basis.
let me just make a point, I don't think that Jally's are going to be as popular as singles (or even little singles) but let's assume half of what they sell if Jally's and they sell 1000 of each them and Singles.
Jally: 1000*4.5 = 4.5TH
Single: 1000*8*7.5 = 60TH
Total: 9000 Chips for 64.5TH
Average per chip: 7.16GH/s
Impact of shipping half Jally: 4.5% total hashrate reduction.
It does not matter because it's a small margin and it's something that will be breaking in our favor, but unpredictably. There are so many errors larger than 5% in guessing this stuff that you are better off just assuming the worst.