Direct communication channels compare

e-mail
SMS
web push
WhatsApp
Direction (in automation)
one-way
one-way*
one-way
two-way
Measured
yes
limited
limited
yes
Personalization
yes
limited
limited
yes
Price
low
high
low
moderate
Privacy restrictions
moderate
high
low
high
Message length
high
low
low
moderate
Rich content
yes
no
limited
yes
Deliverability
moderate
high
high
high
Open rate
low
high
low
high
CTR
low
moderate
low
high
direction (in automation)
E-mail
one-way
SMS
one-way*
Web push
one-way
WhatsApp
two-way
measured
E-mail
yes
SMS
limited
Web push
limited
WhatsApp
yes
personalization
E-mail
yes
SMS
limited
Web push
limited
WhatsApp
yes
price
E-mail
low
SMS
high
Web push
low
WhatsApp
moderate
privacy restrictions
E-mail
moderate
SMS
high
Web push
low
WhatsApp
high
message length
E-mail
high
SMS
low
Web push
low
WhatsApp
moderate
rich content
E-mail
yes
SMS
no
Web push
limited
WhatsApp
yes
deliverability
E-mail
moderate
SMS
high
Web push
high
WhatsApp
high
open-rate
E-mail
low
SMS
high
Web push
low
WhatsApp
high
CTR
E-mail
low
SMS
moderate
Web push
low
WhatsApp
high

* in most cases