Liquid feed is quicker that solids that must dissolve. You can see the first results of liquid feed the following day in warm weather. Liquids are easier to apply evenly and without possible scorching, as can happen with solids if unevenly applied. But solids are cheaper.
I purchased Miracle Grow Lawn Feed. Is this suitable to use now, or should I get a spring feed. Is liquid feed better or worse than granular feed?
There is not much point in feeding a lawn until temperatures rise, otherwise it can be washed away by rain. But this is the time of year to use a feed, usually in late March. The feed you have is fine.