The difference between them is mostly in the CPU and layout of the hard drive. CPU wise, the i7-7700 is a solid processor on a laptop. It offers hyperthreading The 8gb of extra RAM is definitely nice, but you can always upgrade it if it becomes a bottleneck.
CPU wise, the i7-7700 is a solid processor on a laptop. It offers hyperthreading while the I7-7300 does not. The i7-7300 also runs about 300mhz slower in turbo boost mode.
The hard drive configuration is also a bit strange. The i7-7700 one has a smaller SSD, but a larger spinning drive for storage. You can pick up a 500gb SSD (in both M2 NVME and 2.5inch SATA configs) for $100-150 to expand how much storage room you have while keeping it all on SSDs. So for the i5-7300, you'd get the 256gb SSD and then add a 500gb SSD for even more storage for an extra $150 tops.
If you use the 1TB non-SSD spinning hard drive, it's going to be slow since it's a 5400RPM drive...the slowest one. The i7-7700 has a 128gb SSD, which is going to be used up by Windows + 1-2 programs/games...so you're probably going to have to upgrade or replace it anyway.
The i5-7300 also has an IPS screen and the i7-7700 does not. This would give you better color accuracy and viewing angles in most cases.
Sorry if all of that is confusing, I started rambling at some point in there...but long story short, it seems that the i5-7300 Dell is the better buy -- even with the slower processor. 8GB of RAM costs like $85 for this thing.
If you end up buying the i5-7300 and want to upgrade it, PM me and I'll give you links or the names of the actual components to buy. Upgrading it RAM and adding the hard drive is also really easy to do, but if you're not comfortable, you can pay to have the Geek Squad install it for you.
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I am not a Best Buy / Geek Squad employee. All comments and opinions are my own.