Is creating GPG keys with MailVelope as secure as using a program?

[techlist at 123mail.org]

I installed MailVelope not long ago and I was wondering if creating my
GPG keys with this extension within the browser is as secure as
installing a GPG program in my computer to do this and then import the
keys.

I also see that key creation settings in MailVelope is fixed at RSA
4096bit and it can not be changed. But this is fine, I don't really care
about settings, I am only concerned about security.