Training wise, it depends on if you want to endure three years of medicine or years of surgery training...
I'm in one of the integrated vascular surgery program, and we only do about 2 years of gen surg and then a 3 year vascular surg fellowship. You can also go the 5 year general surgery route.
Cardiac and vascular disease are the leading causes of death, the population is growing older...so either way there will be a demand for BOTH fields. That shouldn't be a deciding factor. There are 10+ jobs for every vascular surg fellow graduate because of the demand.
Both cardiologists and vascular surgeons perform several endovascular techniques. Some fields currently (emphasize currently since things can always evolve or change) own certain procedures. There is also overlap..
Endovascular wise:
Cardiologists: coronary arteries/iliacs/carotid stents
Vascular surgeons: endovascular repair of AAA, stents of leg arteries/iliac
arteries, carotid stents
For emergency calls:
Cardiologists: deal with MI's and end of going to the cath lab
Vascular surgeons: deal with ruptured aneurysms/pulseless limbs/trauma
cases (GSWs) and end up going to the OR
Hope this helps...