No one is using a 14" thin and light as a render box. Those additional cores will rarely prove useful unless you run cinebench all day on your ultra portable. Leaks have indicated the Xe IGP is faster than AMD's current IGP and I fully expect Tiger Lake with it's improved 10nm process to have a distinct per core performance advantage over Ryzen 4000 which will make it faster in every day use. Also, Acer's website has the 4700U with a maximum of 11 hours, while the only 14" Intel i7 model is rated at 12 hours. So, don't know where you are getting battery life for the AMD model. Looks like a performance sweep for Intel, along with a higher price.
I don't agree that "no one" is using a 14" laptop as a render box. While I don't think the number is high, I think you should be aware that people nowadays look for a laptop that is as thin and light as possible. If your job is to process video and photos and need to be on the go, I think it makes a lot of sense to get a light laptop that is as powerful as possible to complete the tasks. The extra 4 cores and 8 threads on the 4800U can be of great help here.
Leaks have shown that Xe iGPU is faster, yes. But I rather wait for official reviews than relying on leaks to determine the performance of Xe. There are a lot of unknown as to the specs/ test bed in these leaks. From the looks of it at this point, I feel both Vega 8 and the fastest Xe iGPU should be pretty close in performance. Graphic performance can easily be manipulated by using faster ram, thus, skewing the results. I would be interested to see how each of them perform say at DDR4 3200, and less so of the more expensive/ exotic LPDDR4 (exotic because not many laptop models will utilize these).
Looking at existing 10nm (I am using an Ice Lake laptop btw), I am not expecting Intel to pull a miracle with their supposed 10nm+. I do expect IPC improvements, but its going to be evolutionary, rather than revolutionary. If there is anything we learned from Intel's 14nm, the extra plus, seems to point to improvement in clockspeed, rather than efficiency. Thus my take is while IPC should see a good improvement on Tiger Lake, I don't expect them to close the gap between 4c/8t and 8c/16t significantly.
As for the battery life, again, I think best to wait for official reviews. PC makers can rate anything they want, and by now, we should be aware that whatever they quoted, they miss it by a signficant margin when we are actually using the laptop. At least at this point, most Renoir laptop reviews have confirmed that the battery life is good or very good, depending on the laptop battery capacity.