It’s almost always better to capture a noisy image than a blurry one. Motion blur is usually unrecoverable, whereas noise can often be cleaned up effectively with today’s powerful denoising tools. If boosting ISO helps you get a sharp frame, it’s worth it. Some modern sensors are also ISO invariant… meaning that shooting at a low ISO and underexposing, then lifting the shadows in post, results in similar noise levels to shooting at a higher ISO with correct exposure. For example, an image taken at ISO 800 and brightened later can look very close to one shot at ISO 6400. That said, not all cameras are fully ISO invariant, so it’s helpful to know how your specific camera behaves. But in general, a sharp image with noise will almost always be more usable than a blurry one.