Having had scrotes use 42" Irwin Record bolt croppers to cut my Pragmasis 11mm chain (no reflection on their chain, I bought two 13mm as replacements) I would avoid ground anchors, personally.
The technique I've seen (on YouTube etc) is to get a low section of chain in the cutters jaws, place one handle on the floor and the other in the air. Scrote jumps up and puts full bodyweight through arm in the air. Unless the chain / anchor is completely inaccessible then this is a risk.
Alternatively, if you hang them up and put the chain high, e.g. off the roof or trusses it means the only leverage they can get with cutters is above their heads, pushing hands together i.e. much less. Therefore, chain is harder to cut.
Then again, battery operated grinders are pretty easy to get hold of nowadays ......
OTher's opinions may vary and your circumstances may / may not allow some of the suggested.
Personally as well I find long lengths and heavier duty chains a right PITA. To me the 13mm is about bearable. Pay lots for the padlock too (typical weak link) such as Squire Shielded at c.£50 each.
I got my garage wired to the house alarm in the end and dusk til dawn lighting (waste of juice!). I think you can get little DIY alarms that can be fitted in sheds.
Given I've been burgled twice (once garage and once house) whilst actually in bed then, whilst many ignore alarms, I'd rather have one so it wakes me up.
Something to bear in mind when planning security is that a thief won't give a shit what they break or damage in the process of nicking something (IMO). It's a different mindset to you an dme who usually think about how to do something and how easy it'll be to repair afterwards.
Burglars are scum.