Are you using Handlebars?
I'm not shure what {MREGEFIELD defect} means. Is defect a property of MREGEFIELD? I.e. MREGEFIELD.defect?
I don't think Handlebars has a comparison helper out of the box. #if can only check if a value is truthy.
I'm using the npm package "handlebars-helpers" which for example includes #eq for comparing values, like below. If your use case is a one-off it's probably easier to just write a function. Are you using JSReport Studio? In that case it's really simple to write a comparison helper function in the helper pane and call this function from Handlebars.
Here is how your comparison could look like with #eq.
{{#eq MREGEFIELD.defect "New"}} Yes {{else}} No {{/eq}}