Apichat.io

Not an Official Whatsapp Partner.

Advantages:

1. It can be cheaper for a high volume of messages and especially if you send attachments.
2. Simple enablement.
3. You can see all conversations on phone where you have your Whatsapp app.
4. Offers extra features that Gupshup doesn't have.

Disadvantages:

1. It is not an Official Whatsapp Partner.
2. If you use Whatsapp web, it will disconnect this service. You can do it, but it is recommended only in emergencies. You will be able to reconnect to service from Odoo.
3. You must keep phone connected to the internet.

Choose if:

1. You trust your contacts will not report it as “SPAM”.
2. You want to continually start conversations and trust your contacts.
3. You want to send attachments continuously.

GupShup or Chat-api

Official Whatsapp Partner.

Advantages:

1. It is an Official Whatsapp partner.
2. Whatsapp blocked risk is almost null.

Disadvantages:

1. You must have a verified Business on Facebook.
2. Commissioning the service requires extra steps. It may take 3 days.
3. You cannot use Whatsapp on your cell phone or web.

Choose if:

1. You don't want to put your WhatsApp number at risk from being blocked for any reason.
2. You will be writing to numbers that have not been written to before and therefore there is a possibility that the people you are writing to will report it as “SPAM”.
3. You will only reply to messages and also not send attachments, it can be very cheap.

GupShup fee see here