The connection time would only be a deciding factor for me if all other things were equal. The bus ride is only a few minutes. As an EXP, you have Fastrack access.

Also keep in mind that flying BA longhaul into LHR gives you access to the spa in the arrivals lounge -- you'll have to enter the country to enjoy it, though. You can't use the same services in the airside lounges after arrival. IMO, it's worth it for a scalp/neck treatment in the massage chair.

All of that said, I won't be flying BA until the hygiene issues have been resolved in the T5 South lounges and that has been confirmed by inspection. There are other ways for me to get to India on oneworld.