As far as duties are concerned, the techs at the hospital I intern at have varied duties. Sometimes they spend entire shifts working in the IV room doing admixtures, preparation of cytotoxic drugs, and some hospitals they do total parenteral nutrition (TPN) prep work as well. They might also do some courier work, do cart fills, blister pack oral unit doses (usually in smaller hospitals), work on the Pyxis Medstations (restocking, inventory, etc). In other words, hospital is quite busy work (usually), and much more diverse than the usual retail establishment.
The downside is that you are essentially doing work that might not benefit you quite as much in terms of experience as it pertains to pharmacy school. All the techs I know who worked retail have a decent undertanding of their generic/trade names, usual dosages, even indications/contraindications, and side effect profiles and black box warnings...they did work in medium/high volume stores like Wags. Most of them have worked quite a few years as techs prior to pharm school and seem to have an intuitive knowledge of pharmacy administration and pharmacy computer systems. Not only do they routinely see the top 200 drugs, they see and meet the patients, and read their scripts. The few pharm students I know who worked almost exclusively as techs in hospital don't quite have that breadth of knowledge. In retail, there is a connection between the drugs you help dispense and the patients you meet. You start to know stuff about the medical history of regular patients, for example. When you do tech work in a hospital setting, you are pretty much disconnected from the patients. You don't really know who the patient in "Room XXX" is, or what the IV admixture you're prepping is really for (since you're not looking at their chart). As it is, I usually keep a copy of "Tarascon Pocket Pharmacopoeia" in my scrub pocket to fulfill my curiosity about something I'm preparing for a patient...if I have time. I guess you can make hospital work as "educational" as retail if you put in the time and effort. There is a cool charge pharmacist at the place I intern at, who insists that I tell him the trade/generic name of a drug, its class, etc when I give it to him to verify...it makes me stop, think, and learn, even though I'm doing hundreds of IVPBs, syringes, etc.
As far as difficulty in obtaining hospital vs retail, the techs I've met in both places tell me that it is harder to get a hospital position than retail. Makes sense...pharmacies are popping up like gas stations on every corner of the new subdivisions here in Vegas.