This is an actual comparison between Sendgrid and Sparpost, after having actually used both for transactional emails, albeit with a small user base. No marketing talk here; just a developer-focused comparison.
Pros
- analytics for recipient geography, email clients & devices, mailbox, and browser type
- drag'n'drop visual email template designer (see limitations and issues below)
- can have multiple versions for a given template, and marking one as "active" for use
Cons
- No CSS inlining
- Misleading status responses. When sending and email and the template fails to compile, the result is "success".
- Status response doesn't include anything useful.
- Vague, unhelpful, error messages
- Slower web app than Sparkpost
- Disjointed support, with one Twilio team member not bothering to re-file a bug report to the correct repo, but instead asking the bug reporter to do even more work
- Can't schedule emails more than 72 hours in advance.
- The visual email template designer doesn't allow customizing the social media module, which includes a fixed set of social media links. It appears imposible to add, say, a Discord link.
- The email Activity doesn't show the body of the sent emails.
- Previously confusing API, until a random contributor rewrote it in 2017
Free plan
- 100 emails/day
Pros:
- AMPHTML support, for dynamic emails
- CSS inlining, critical for Protonmail and possibly other providers
- Much more powerful template language than Sendgrid's crippled Handlebars (which is already handicapped)
- Sending an email returns a useful ID in the response
Cons:
- no analytics about recipient geography or email client time; only opens/rejections/bounces
- Plain HTML template editor, with an odd page about it (2020-May-01 mirror). Instead, they recommend a separate tool for visually designing emails, Topol
- Awkward error message display when compiling templates
- Template errors are listed backwards
- Template editor has no undo
- Can't schedule emails more than 72 hours in advance.
- The email Activity doesn't show the body of the sent emails.
- Their support system is rudimentary and home-grown, basically a contact form. You can't track the status of your tickets online, and the "Support ticket closed" emails are useless (they only mention a case number, which you can't look up anywhere). This is puzzling, when there are plenty of decent ticketing systems (Zendesk, Freshdesk etc.).
Free plan:
- 100 emails/day