Needs, needs, needs. Everything is dependent on that.
How much will you be using the car in the first year? How much walking? How much time on public transport?
What are your longer term plans for childcare? Will you be taking them to nursery in a pram that needs to stay there?
So many things factor into it - though most annoyingly, you generally only find them out when your child is about 3...
I know a lot of people who have sworn by their iCandy or similar and yes, they are lovely prams. But (and this is just personal experience) they were either mostly SAHP or they used the car for the nursery run. Once your DC is 1-2+ travel systems can sometimes become quite heavy to push around compared to a little umbrella stroller, so I say either SAHP because they have more time to walk slower with the DC walking alongside them, or if you use a car a lot then a travel system can be very handy.
On the other hand, the parents I know who had to use the pushchair for the nursery run very swiftly changed to an umbrella stroller than was lighter, easier to fold and, realistically, it mattered less if it got a bit bashed etc in the nursery shed.
I'd always say if you think you could afford, say, £600 on a travel system, don't spend it all unless you are 100% convinced that it really will last 3+ years. If you're not, spend £400 and then make sure you can afford later to change pushchair if you need to.
Fwiw, we had a Maclaren Techno XLR, their top-of-the-range, lie-flat, from newborn pushchair and absolutely adored it. Got rid of the much hated pram/travel system at 3mo and changed to this and used it endlessly for 2 years until DC got heavier to we moved on to cheap, light 'holiday' strollers for the nursery run. Expecting DC2 now and will just buy the carrycot attachment for the Maclaren and use that again.