So there are lots of reasons you can get different results, but for most home users there is no need to spend £1000+ on a 4G router, but donít expect a £100 4G router to match the performance of a £800 - £1000 smartphone.
No need to spend as much as an S10 or iPhone XS to get a modern LTE radio in your device. The problem is that most home routers are as you said Cat3 or at best Cat4, so do not really handle CA or the other modes of LTE-Advanced.
All 4 networks in the UK have CA deployed depending on area. Even my local mast for EE went from 1x20mhz to 1x20mhz+1x10mhz in the last three months. My old iPhone SE can't take advantage of this, nor can my legacy Vodafone USB dongle.
However the Huawei desk mounted LTE-routers are often under-spec for the price, you can easily get more capable LTE radios in similarly "cheap" devices. Much of the problem is the free devices supplied by the networks are likely old stock!
for example is only Cat3/4 but this Huawei
is likely better looking at max speeds.
But actually this Netgear
unit for £297 covers Gigabit LTE so is pretty close to the performance of the S10 / iPhone XS and a lot cheaper.
It pays to do your research as always.
80/20 (2/jun/14) at 470m - Sync history highest: 64/9 (Sep/17), 54/6 (Jan/19), 51/6 (Mar/19)
20 years of broadband from 1999's ntl:cable modem trial - Live BQM