Which to buy Domane SL5 2019 @ £1k Vs gen 4 @ £1.7k?

Been looking to get back on a bike after several years of doing nothing! The kilos/pounds have piled on. 🙁

Initially I considered a Domane AL 4 but since it is out of stock at the local dealer they are willing to do a deal and offered me the SL5 gen 4 for the same price as the AL5. That is to say £1700.

Went home to think about it (was considering Cannondale Synapse) as the dealer kindly offered to keep the offer open.

In my research I found a 2nd hand 2019 SL5 model for sale for £1k. New tyres, redone hydraulic fluid and cables, plus handlebar grip.

So, my question, is the newer model SL5, and the Trek dealer (official Trek store) service around it worth the extra £700 in the hivemind's opinion? Think buying new includes 2 services worth £100 each apparently.

My expected use will be regular commute type of riding, shopping etc plus some 10mile rides around my home (leafy Berkshire by the Thames) and perhaps, hopefully, some longer rides to up my fitness.

Keen to see what the group thinks as you all have far more knowledge in this area. Plus, the Kia Niro EV group helped me push the button on my car purchase and I am delighted, so I hope for good things!