Ok, I'm looking for some recommendations here.

Specifically, I'm looking for a handheld GPS that I can use primarily when working out in the field as a Ham radio volunteer at trail runs etc.

Worst case scenario, need to call in an airlift or a SAR team and I need to be able to give them accurate coordinates and/or trail location and possibly help locate a safe landing zone.

Should I get something with topo map capability or will something else suffice?

I've looked at a couple of Garmin's, the Legend HCX, the Vista, etc.

They all seem to be very similiar in features, I think I need something with a relatively easy to use additional memory card feature so I can load a topo map.

I can't seem to find anything with the topo feature already installed, is that accurate or have just not searched enough?

I don't mind spending a bit of money but I don't have a limitless budget.

Any thoughts?

I would see if you can rent a bunch from REI at once and compare Pick the one that works the best and does what you want.

The Colorado and Oregon series have some that come pre-loaded with Garmin's topo maps, IIRC.

Personally I've used many GPS units in the eTrex line and the 60Cx model. The 60C(S)x series is great & tough, but a little bulky. I went ahead and changed to an eTrex Vista HCx for the space savings.

Garmin offers units pre-loaded with mapping software, or you can buy it on a memory chip, or else buy the CD/DVD and manually load the maps onto the GPS unit of your choice.

You definitely want one of the Garmin units with a "high sensitivity GPS chipset" so you can get a better satellite lock in iffy areas (forest, canyons, etc.).

If I understand correctly, you're looking for a unit with 2 memory card slots? Why would you need that? I own a Garmin Legend HCx and I've got currently 3 different maps loaded on my 4GB memory card. In any case, switching memory cards is really simple if there's absolutely no other way around it.

I think there are considerations on where you'll be. Do you need a topo map to give your GPS coordinates? I don't think you do. You don't need a map at all if the GPS displays them. If you want to locate a safe landing zone, and you're in a city, a topo map won't help. It would out in the wood, I guess, assuming you can read it. :-> Frankly, if the rescue team has your coordinates, I'd expect them to be better prepared to locate and land at a safe place.

I have a Colorado 300 which comes with no maps, and I've loaded it with free ones that I find on the Web or that others prepare. The 400t comes with a topo map, but I don't know if it's the right area for you, nor if the scale would be useful.

I live in an urban area with lots of trail runs, bike rides, etc. for fund-raisers, and my view is skewed by the nearness of roads to the trails. I've had a chopper called once for a volunteer evacuation, but it was to land on an intersection of two paved roads near the accident. Are you seriously out in the field with no roads? I also have a Nuvi with city maps on it, and that gets me through all my 'field' operations here in this area. (The colorado 300 is for Death Valley, Burning Man, and the like.)

My thinking is I'd ask other volunteers if they use a GPS and what; get several opinions. My other thought is, I'd ask the SAR guys what they'd recommend.

Hmmm...not sure how you got that idea but no, I don't need 2 card slots, I'm not even sure if I need 1.

That's what I'm tryin to figure out. It seems that Garmin offers either internal memory of 24 mbs or the option of using microSD cards to increase the map capacity.

For those who use a memory card GPS, any issues arising from the use of the cards?

Likewise, for those using only the internal memory, what kind of detail can you get on the maps and how hard is it to download new maps?

I've sorta narrowed down my choices to either the Vista HCx which uses cards and has a built in compass and altimeter for $235 or the Summit HC which uses internal memory and also has the compass/altimeter for $180.

I've also found a Legend C with internal memory and no compass for $130.

I don't think that the Legend has the newest satellite acquisition ability in it for that price.

Thanks for the help so far. Keep it coming!

It appears that the SEARCH capability on ETS is broken as it won't find any threads using GPS as a search term. That's clearly wrong as GPS is a very popular topic.

Here's a recent thread I remember participating in:
http://forums.equipped.org/ubbthreads.php?ubb=showflat&Main=13419&Number=175428#Post175428

Forwarded to the guys who might be able to figure it out.

For the garmin legent/summit/vista get the H model, it has the newest extra sensitive chipset. 24M isn't a lot of memory for maps so I'd personally get one with the x. I have a Legend HCx and a 2G MicroSD card in it. I bought Garmin's City Navigator and was able to load the 48 states then all the topo maps east of the Mississippi with space for lots of log files left over. I set it to always log and store the logs on the card so I can have them default to .gpx files and not be limited, they truncate the logs on the internal memory to a certain number of points.
I load it up with a pair of Sanyo Eneloop AA's and have used it on and off for several days without needing to swap batteries.
Bought the bike mount most recently

JohnE, I would recommend the new Garman Etrex HCX series, or the 60Cx model as well, the HCX has a awesome battery life and I have street,marine and topo maps loaded through a series of micro sd cards of most of the world. It's a small travel unit with common batteries (2 AA) and has been very dependable. I'm eager to see the new Garmin Dakota 20 coming out shortly to see how that fares.