A blog is something you use at the top of the sales funnel (TOFU) to create awareness around the products and/or services the company provides. You do not promote products or services, you just create awareness around the problems your persona has. The other main goal of a blog is to generate traffic from organic search or social media.
The end goal of the TOFU part is to move a visitor towards a landing page or an opt-in, so you can make them a lead. You could also build your retargeting list in Facebook or Google, so you can remarket to them. I.e. you want to own the traffic that comes to your page.
A newsletter is a part of the middle of the sales funnels (MOFU). You already have created awareness around the brand, products, and services. This is the part where we generate leads and nurture them into buyers. The KPIs here are different. You must look at leads generated, conversion rate, engagement on email opens etc.
The end goal is to sort out who are the sale’s qualified leads, and who are not (usually about 25%).
So to sum it up: Blogging is for snagging potential customers and a newsletter is for converting them and retaining them.
Thinking about the next step? Well, Ireland Website Design can help you with your marketing and work with you to create engaging newsletters and blog posts.