Hey Sarup!
I'm one of the makers behind InviteRobot. Obviously, I'm biased. Still, here's what we tell users who ask us what are the main differences between InviteRobot and Launchpass.

Although we ultimately share the same goal, there are 3 main differences:

1. We believe that professional communities have more advanced needs than preset pages.
   With InviteRobot, you keep control of your layout. You don't have to use our landing page. You implement the payment widget on any page you want, your blog, your website. You can trigger the widget using any custom buttons or links, which gives you the flexibility to add it in complex HTML layouts. E.g. you could have 1 button per plan, like on remotive.io/community/.
   You can also create advanced pricing plans, with as much recurring or one-off options as you need.

2. One of the main difference with Slackpass is our pricing model. You'll notice they're more expensive.
   And we do know starting a community is loooong, so we offer the first 15 members for free. No time limit.

3. Feature-wise, there's one big difference: InviteRobot works at the Slack team level, whereas LaunchPass can work at the channel level. This means that if your community consists of multiple Slack channels, or members can create new channels, then InviteRobot is the easiest way to get started. OTOH, if you have a (free) public Slack team, with a (paid) private channel (e.g. a "premium support" channel within a public Slack community), then Launchpass will be better suited.

TL;DR is: We want to make it easy to start new communities.

FYI, we're a small team, bootstrapped, and very purposely chose independent makers as our audience — because they are the people we like to serve, and because we ourselves are independent makers. We also make other apps which revolve around Stripe, like cashnotify.com/ — a macOS app to get your Stripe notifications in your menubar (and very soon, Windows + PayPal).

If you have any specific question, let me know!
Julien