Hi there! We always say that any experience you include in your application must show two things: Commitment and Progression. These are usually achieved when you do an experience for a significant amount of time, so 1 or 2 labs is definitely better than many more. Additionally, spending time in just one or two labs will give you the opportunity to get strong reference letters because, by the time you have to ask your referees for a letter of reference, they will know you well and will be able to speak to your skills and essential qualities. Having a diverse research experience is always a good idea but, when it comes to med school applications, quality is better than quantity, so keep that in mind!