As a seasoned Sales professional and CRM developer I have grown to learn the majority of the players on the market to date. The first thing you must do is evaluate what is it you want from a Sales CRM and to find this out you will need to discuss it with your sales team and account management team.
Each will have their own wants and requirements, yet they will typically fall into similar ballparks.
Here are some of the likely requirements they are going to ask you for:
Pipeline. Seems obvious but how versatile the pipeline is, makes a difference. Can you edit it, can have multiple ones if that's what's needed, can you customize the deal settings, can you customize the reporting, etc.
SMTP configuration. Again seems obvious but not all do this and some rely on BCCing your email which does work as effectively or looks as professional. You also want to be able to track email opens, unsubscribe and track all email activity in the deal or contact on the CRM.
Automated follow-ups, also known as Sequences. This is where you can create a series of emails all on autopilot and if any salesperson wants to be efficient will have several set up for all types of scenarios. They will also want to be able to incorporate calls, maybe text messages, and calendar booking systems. Again some do some of these things and others do it all.
Team inbox. You might have a company email on the site and it can become very annoying to manage this email for the team unless delegated to one person, but even then what happens when they go on holiday, etc. Ideally, you have a CRM that enables a team inbox that everyone can manage, delegate, and mark as complete.
Built in-call feature. Again some have it, others have it as a built-in extra, and some not at all. Also, some are terrible. You will want to test this before signing up. Also, see can you use your own number or you need a new one, can you do text messaging, can you do it from your phone, etc.
Task management system. Again these vary a lot, some are just lists, some are only visible from the deal or contact and some make you manually perform actions and just tick them off. Others, however, will let you do it all from a single screen and actually automate your work for the day taking you from one task to the next without any effort or thought. These are the ones you want.
Calendar booking. Some integrate with things like calendly and others have their own built-in and directly sync to your work or personal calendar. Make sure to check as this can save you another subscription a month and changes your overall software stack.
Reporting. Most sales agents won't care about this except from an open rate point of view. Your managers however will want this for sure. You will want one that can monitor all your KPI's for productivity, pipeline, timeline to sale, and conversion rates.