Vista HCx was my first GPS. I have been using it for about a year now along with my iPhone. I use my iPhone for reading descriptions of caches, recent logs, hint if needed and to submit field notes. The latter is important to me especially when doing a lot of caches in one day. I love submitting logs whilst out in the field rather than doing them back at home. Today, I even received an email from the owner of the series of caches whilst I was still out in the field!
The Vista HCx is a great GPS. I find it very easy to use.
I recently purchased the Oregon 500t. Why? Because I want better maps. I wanted to see exactly where caches are on the footpaths rather than using a real map and guessing. I bought the GARMIN GB Discoverer 150K Map Card for this. Haven't tried it out in the field yet as it only arrived today after I got back from a series of caches. However, what I have seen so far I am not too impressed with the GARMIN GB Discoverer 150K Map Card . It is very slow to load each section. (The topo map that comes with the 500t is much faster but doesn't show footpaths)
I can write field notes on the Oregon but I find it slow going and I have to wait until I get home to connect the device to my computer to upload. It is far quicker to type on the iPhone and it uploads straight away.
My Vista HCx never agrees with the Oregon regarding distance to cache. Even the trip computer on both differred. I will need to study them both more. Maybe I am not using the Oregon right?
For me, the iPhone is an important tool for my geocaching. I could have stayed quite happily using my trusty Vista HCx. My Oregon, well it is early days yet, I love it but is it worth the money? Only time will tell. I have only had it two days and only found 27 caches with it.