Spanish citizens can travel to 188 countries without a visa or with a visa on arrival. As of Q4 2021, Spain is rated 4th in the global passport ranking.
Please be aware that naturalisation process takes 10 years of living in Spain.
A Malta passport is your ticket to 184 countries which is not a big difference. However, you can apply for its passport under Malta citizenship by investment program in just one year after obtaining a residence card, i.e. 10 times faster.