The Dell should have a superior processor, though it may not be as efficient with regards to battery life as it is a higher thermal power dissipation rating (45W as opposed to 15W for the AMD). It looks like AMD has done better with its newest mobile CPU/GPU chips, which in the past were outclassed in most respects by Intel's offerings (aside from niche cases where a user wanted the APU for moderate gaming at low cost compared to Intel's integrated graphics chips).
The nVidia GTX 960 on the Dell is probably going to be similar with regards to graphics performance to the R9 M380 on the Lenovo, but the GTX 960 on the Dell should still outclass it if even only by a little.
The biggest factor for difference is likely going to be the solid state drive (SSD) on the Dell vs the standard traditional spinning hard-drive for the Lenovo. Yes, the Lenovo has nearly 4x the amount of storage space, but it will be noticeably slower when booting up, loading programs, and loading games. This difference is going to be more noticeable than anything with regards to the CPU or GPU between these two computers. A good SSD will be able to cut boot-up and load-up times by 2x-4x the time of a regular HDD, so the Dell is a clear winner here. If you absolutely need the space on your laptop, the 1TB is useful (i.e. significant amounts of media, music, etc). However, your best bet is the SSD if you can live with the 256GB and use an external HDD or cloud storage for your back-up and media files. Since the Dell is cheaper to begin with, it is probably your best bet.
Either way, you will probably be able to upgrade the storage on either device by buying a larger SSD if you need (for example, getting a 500-512GB SSD drive to replace the 256 if you need the space. Just make sure you find out what connector the HDD/SSD uses (SATA, mSATA, m.2, etc).
You should also look at weight, size, ports, and battery life to take those into account with regards to your preferences.