If you play campaign the only path is oil only however in utopia mode it really depends on the map.
In the campaign, you can take short term moves that finish resources quickly because the game ends after the 5th campaign. in utopia however surviving the longest is key, however utopia lets you research both settlements and underground resources. In the campaign getting oil is a key part of the campaign so choosing adaptive is basically like going extra hard needing skyways too just to get enough oil and enough population to even have enough workforce.
The generator upgrade only affects the main city generator, all your sub cities use adaptive instead so the choice really is based on wha