Hi,

Additional benefits of Gold over Silver;

First class check in ( useful at LHR T5 maybe not at T1) ; at other UK and European airports Silver is just as useful

Galleries F at LHR ( elsewhere in the UK and most of Europe it is the same lounge if you have Silver or Gold)

Arrivals lounge at LHR T5 after arriving of a BA long haul flight in any class ( arriving before 2pm as it shuts then )

If you go longer haul then you can use First class check in and F lounges of other OW alliance airlines.

I think I found with gold that I could get rows 1/2 on domestic flights in advance .

Where are your longer trips planned ( some of the First class lounges in say HKG or the USA are pretty good)

The main step up is from Blue ( or Bronze) to Silver for lounge access and additional baggage allowance whilst it is a smaller step up from Silver to Gold ( if only flying domestically)
If flying to the US or on AA from one of their airports with a flagship lounge ( JFK/LAX/ORD) then Gold is more useful.

Regards

TBS