Before you switch, be aware that TMobile network has signal limitations or no signal inside building due to weak or lack of building penetrations. TMobile offers cheap price because they have many limitations and offer great service on a small service portions of Verizon and ATT offer. TMobile offers many perks to compensate their subscribers for any inconvenience the subscribers experience.
Also, it is better to ask your trusted friends and coworkers about your question as they are better sources than any commenters here, including myself. I do not work for Verizon or ATT. I used to be TMobile subscriber but changed to Verizon due to many inconveniences I found with TMobile especially building penetration issues and lack of coverage outside metropolitan area.