I could not resist looking at PCs when shopping at Costco, mostly because the internet speed on my old laptop really sucks lately. It is a Dell Inspiron, 8 years old. Anyway, upload speed is between 50 and 100 on WIFI, when tethered to my cell it jumps to around 150. A $500 HP came home with me, upload is about 250! I know some of this can be due to overall traffic, but this sort of difference is really surprising. Is this typical with a new PC? If so the old Dell will go in front of the exercise bike.
Did you check your download speeds? It could be that the bottleneck to your upload speed was your wifi link between the router and that laptop, and the new one can negotiate a faster connection mode with the router than the old one could. Maybe the old laptop was able to get a faster connection to your cell phone than your router. Otherwise I'd have to think it's just a coincidence.
I would also think that you have newer technology in the new PC in terms of either the WiFi protocol or the ethernet card. That also makes a big difference (I upgraded my wifi at home and doubled my speeds)
I work for one of the big hardware companies that makes networking and WiFi stuff, their name rhymes with Wet Beer, you might own something we made.
Roughly every 4-5 years WiFi standards get an upgrade with a bunch of new technologies and features added that, for the end user, amount to faster and more reliable speeds.
To unlock the best possible WiFi speeds your broadcaster (router, mesh system, access point, etc) and receiver (laptop, phone, computer, etc) both need to support the newer standards, and older/slower devices in the system can definitely bottleneck your speeds. Assuming you pay for good Internet (fast hardware cannot make up for a slow incoming connection), a fast router and a slow WiFi client is like feeding a firehose into a drinking straw, a slow router and fast WiFi client is basically the inverse, and so on.
All that is to say that yes, the hardware in the computer makes a difference too. 
download is faster too, but not by the magnitude of upload. The hardware/software upgrades make sense. Incoming signal is ATT wireless, about 2 years old. Not the best but more than adequate for our use. Thanks, the new laptop stays.
