Earlier this week, amid the typical hoopla and mania that seems to be associated with every Apple announcement, the company launched a number of new products, including the iPhone 6s and 6s Plus. Among the features that Apple is touting is the claim that the wireless experience on both Wi-Fi and LTE are twice as fast as previous generations. The exact wording (emphasis mine) on Apple's product page is:
"iPhone 6s features LTE Advanced with speeds up to twice as fast as the previous generation.* It supports more LTE bands than any other smartphone. And when you're connected to Wi-Fi, iPhone 6s lets you do things like browse the web and download apps at speeds up to twice as fast, too."
One important thing to note is that the asterisk points you to a disclaimer on the bottom that states, "Speeds are based on theoretical throughput."
Knowing where network speeds are today, I found this claim to be a bit hard to believe, so I went and looked at the "tech specs" portion of Apple's home page to see what technologies these phones had on them.
For Wi-Fi, the previous-generation iPhone 6/6 Plus shows it has 802.11a/b/g/n/ac. For the 6s/6s Plus, the tech specs show 802.11a/b/g/n/ac with MIMO. From this, it looks like the 6/6 Plus had a late-stage AC wave 1 radio, and the 6s/6s Plus has an early-stage wave 2. The Apple site states that the Wi-Fi is capable of speeds up to 866 Mbps, which is actually comparable to late-stage wave 1 speeds, so no real speed increase over the last device.
The other caveat here is that to actually connect at wave 2 speeds, the access point needs to be wave 2. Wi-Fi vendors have only recently released those, so very few are actually deployed. A customer who bought one of the new iPhones will still only connect at the speed that the current AP allows, which in all likelihood is N or AC wave 1.
Wi-Fi upgrade cycles are anywhere from 18 months to two years, so by the time 802.11 AC Wave 2 is deployed widely enough for most people to actually get a speed advantage, we'll likely be on iPhone 7 or 8.
Regarding cellular connectivity, this is a bit of the same story as Wi-Fi. The 6/6 Plus supported LTE, while the new phones are out fitted with LTE Advanced, which Apple's tech specs page shows as having a transmission rate of 300 Mbps. While it's great that Apple put LTE-A radios in the 6s/6s Plus, the footprint of LTE Advanced today is minuscule and build outs have been slow. Heck, even LTE service is spotty today, as I've noticed even in major cities I'm often reverting back to 3G.
Earlier this year, the French wireless operator SFR announced the availability of LTE-A, and below you can see its coverage map for a French city. Even in the most widely covered regions, it's still possible to end up out of range of LTE-A service after walking just a couple of blocks.
With that being said, every major wireless operator is building out their LTE-A footprint. But think how long it took LTE to become available, and remember that the roll-out isn't even complete. Similarly with Wi-Fi, by the time the LTE-A footprint is big enough to matter to most consumers, we'll likely be on iPhone 8 or even 9.
If you're considering upgrading to the new iPhones and the features like "live photos" and 4K video are appealing to you, then by all means, drop the money and upgrade. However, if you're upgrading it because you're expecting this iPhone to have network speeds that are twice as fast, hold off because you're not going to get it consistently. Apple can claim 2x speed, but read the fine print – those are theoretical speeds. You can't access the internet with theoretical infrastructure, only what's deployed, and that's going to give an experience similar to what you have today.