Well, while I have been satisfied with the sensitivity of the Oreon 400i I have, I think the 62s, which I won also is better. In addition, of all the models you mentioned, the 62s is the only one you can attach an external antenna to, and just that fact might be really important to you. I use my GPS unit for K9SAR and go down where ever my dog indicates. NYS has many wooded areas, some canyonesque areas, but not as deep and narrow as in other parts of the US, so I cannot tell you what will happen your way. But I've been happy with my 62s and while I own an external antenna, I never had the need to connect it to the 62s.
t models are not a necessity. Simply fo to www.gpsdepot.com and pick whatever 24K maps you need for your area. The t models have 100K maps, less details but their advantage is they cover the entire US. So mileage will vary with your use.
