If you need the higher gear a 52-36 provides, an 11-34 cassette is your only option (and the cheaper option).
If you can sacrifice some top speed, a 50-34 chainring is a better option, but more expensive option, as it allows you to keep tighter gear spacing on the rear.
If you need an even lower gear, you can do both if the RD can accept the range.
I'm running a 50-34 with an 11-32 and the cassette spacing was noticeable better on the stock 11-28. I needed the climbing gears though, so I simply got used to it.