Providing you can get on with the comfort of the E2Cs and you can get a tight fit in your ear it would be no contest. The E2Cs would comfortably outperform both the PX200s and CX300s. The Shure balance of sound is much leaner and tighter sounding so this may take some getting used to. They also require a completely sealed fit in your ear to get any kind of decent bass response, however when you do the bass quality and general clarity from them is stunning.
I used to have a pair of E2Cs and liked them a lot but became irritated with the lack of comfort using the standard yellow foam sleeves. The foam sleeves were the only ones I could use and get a decent tight fit. They also got really grubby very quickly too. I have now just purchased a pair of the Shure SE420s and they come with much nicer types of foam sleeves that are black and have a smooth exterior coating on them allowing them to fit more comfortably and the can be cleaned easily too. I would recommend looking at the other models in the SE series which I believe also come with the same smooth type foam sleeves. The SE210 would be an option worth considering at £80 from
here.