Sony 70-200 f/2.8 GM II vs f/4 G II

I'd preface this whole post by saying I'm at best a casual hobbyist - I derive no income from photography, I just take pictures of nature and my family. If I'm really honest with myself - I don't really need more gear. Let's imagine a hypothetical (or impulse buy) scenario where I do proceed with this.

If I did have to buy a new lens, I'd really want to go into the higher focal length zooms. I was in San Francisco earlier this year, and not being able to zoom really close into some distant sea lions somewhat irked me. Even with my Sony 24-105 mm f/4 in APSC crop mode (so effectively 105 mm * 1.5) - I wish I could've gotten closer shots. What could've helped in this scenario is that extra reach I could get from a 70-200 zoom. In my case, I'm really tempted by the the Sony f/4 because

• I'm on a budget - it's not like I'm a wedding photographer and will be able to recoup investing more into better gear
• I can use it as a macro lens
• Under very low light conditions, f/2.8 vs f/4 isn't that big of a difference - in those scenarios, I might as well reach for my 50 mm f/1.2. A really good prime lens with a lower aperture value will let in way more light, so under bad lighting both lenses are not great. When the sun is out and the sky is blue - I'm not going to pretend to be snobbish enough to think f/4 isn't good enough.

Probably worth noting - Tamron and Sigma also create decent lenses that are high on quality (not necessarily reaching Sony GM levels - but I'd say definitely G levels perhaps) and much more affordable. For now though, and I won't get into all the reasons, I'll stick with native Sony glass.

Arguably this whole f/2.8 vs f/4 debate applies to other focal lengths too. Heck, even at the middle zoom tier, I have the 24-105 f/4... if money grew on trees, sure, I'd be interested in replacing that with the Sony 24-70 f/2.8