I would think this one hangs very much on what you consider 'pleasant'. The cross-platform change at Earls Court is certainly more convenient than changing at Hammersmith, but I'm not sure I'd rate it as more 'pleasant' - especially since the Earls Court platforms are usually very crowded.
Another relevant factor is the H&C/Circle line between Paddington and Hammersmith is almost entirely above ground - and elevated in sections, so there is quite a decent view. Going via Earls Court means almost the entire journey is in tunnels, and the non-tunnelled bits are in cuttings, so no view of anything besides the walls of the cutting. And I quite like Hammersmith H&C station: To my mind, it has a rather quaint, quiet and genteel feel, which is unusual in tube stations outside the suburbs.
