www.kraytracing.com

Much better! Still a bit repetitive though. Needs more patchiness and flowers IMO.

Most importantly, there is a vertical tree right in the centre of the image, which composiotionally is a really bad thing to do

Much better but need to fix some problems.
Check my draft:

1.- need to delete halos to all 2d vegetation, whith this you can remove the black border or vegetation and take a nice integration.
2.- Control saturation and ilumination of your 2d vegetation and correct to match whith your scene. this reduce 2d impact.
3.- Move some element blocking the view of the image, try to not hide important element, and don´t place big object in center of scene.

Also, the alpha map cars are too sharp, and need softening a little. Personally I would remove the vegetation from the balconies. They are too repetitive and this is a real giveaway in a render. There are 6 of these and they all look the same. If you can see more than 1 identical tree or shrub, you have spoiled your effect.

thanks. I will treasure your advice.