Why, Martin? Was this before chillers like the Hydra came out, or for some other reason? I shied away from a plate chiller given issues of clogging and cleaning--not an issue for you?
To get reasonable performance out of an immersion chiller, either the wort or chiller needs to be moved. Since that occurred 'pre-pump' for me, I had to constantly move the chiller around in the kettle.
I do have an excellent wort inlet system in my kettle that prevents any large particles into the wort stream. My wort is virtually crystal clear entering and existing the plate chiller. That significantly reduces my worry level regarding contamination.