I am partial to my puretone cardiology. It seems to give me a better sound quality than the littman, but i suggest whatever works best for you. I have known people that could hear great using an el cheapo and couldnt hear anything using littmans or the like. so just find what works best for you.
I use a Littmann® Electronic Stethoscope Model 3100 since 3 years when i examine my patients at my icu, it is simply perfect for that job. But for the prehospital work i prefer a Cardiology SE because the electronic part needs to much time to run properly when I or the patients needs a fast decision. Whatever you choose or prefer for treating your patients, remember the most importent thing on a stethoscope is the part BETWEEN the eartips.... ;o)