Thank you so much for your comprehensive and helpful analysis.
I am good at c++ programming, also have some experience on Java and .NET. But I don't have any experience in consulting service. That is why the Medical Device provider offers me much better salary than the consulting firm.
By the way, I made a mistake in my previous post. I mentioned that I would serve clients in Financial sector. Actually the consulting firm puts me in the Resource operating group, which specializes in the energy, oil, gas and utility sector. Anyway, mainframe and IT modernization technologies can be applied in any sector. I may work for clients from various industries.
Thanks again for your kind advices. I will take them into account seriously.