Hello Sakshi,
Your main concern seems to be about the Work environment.
It all depends on where you are working and how much patience you can have with your patients and your own profession. As you seem to know that the Cardiovascular technicians have to work more but they also earn well.
They have to spend a lot of time walking and standing. Heavy lifting might be involved to move equipment or transfer patients. Those who work in catheterization laboratories might face stressful working conditions because they are in close contact with patients with serious heart ailments. For example, some patients might encounter complications that have life-or-death implications.Some cardiovascular technologists and technicians might have the potential for radiation exposure. However, exposure is kept to a minimum by strict adherence to radiation safety guidelines, such as wearing heavy protective aprons while conducting certain procedures. In addition, those who use sonography can be at an increased risk for musculoskeletal disorders but improvement in technology is reducing the risks.
Whereas, The  Noninvasive technicians are the ones who specialize in Echocardiography or vascular technology. Tests are called "noninvasive" Because they do not require the insertion of probes or other instruments into the patient's body. Technologists view the ultrasound image on a screen and may record the image on videotape or photograph it for interpretation and diagnosis by a physician.

Above all, It should solely be your own choice that where do YOU want to give your valuable service and time.
All the best! :)