Vostro 5502: SSD upgrade/exchange

I am sure you will receive a number of replies on this. But in order, You can go as large as 4TB in storage size (PCIe). Gen 4 are backwards compatible so either Gen 3 or Gen 4 would be fine. There are heat sinks available at Amazon for instance, which will help keep the SSD cooled down. And there are many good brands such as Samsung, Crucial, AData and their XPG, Kingston, Western Digital just to name a few.

To add a couple of points:

PCie 4X4 drives will only run as fast as the system allows (which will be X3 on this notebook).

In general, the higher the performance, the higher the power consumption and therefore the higher the heat level will be.  Check the power requirement for any drive you wish to purchase -- the lower, the better from the system standpoint.  There are gaming SSDs that can draw over 10W, and there are high performance drives that use 3/4 of that at most -- the latter are preferable.

The higher the power draw, the hotter the drive will run, which will compromise battery runtimes and ultimately the longevity of both the system and the drive -- or, the drive will simply throttle itself back if it has a thermal management algorithm (most do) -- which will in turn negate any advantage of a high performance drive.

Initially I added a 500Gb Samsung EVO 970 Plus to the second NVMe slot in my Vostro 5502 for Linux Mint.  I left the factory Adata SSD in slot 1 for WIndows 11.  The Samsung drive benchmarks at double the speed of the Adata SSD (~1500 vs ~3500).  As time went by I wanted some more storage space so I replaced the Adata SSD with a 1Tb Samsung EVO 970 Plus.  This SSD was partitioned to 500Gb for windows 11 and 500Gb NTFS shared general storage partition for Window and Linux.  It was immediately apparent that the Samsung SSDs use less power than the Adata SSD as I saw an increase in run time between battery charges.  I want to say maybe a 10 to 15% increase in battery life.  It was noticeable.  I'm quite pleased with these Gen 3 SSDs, they are faster, I now have more storage, got a free battery upgrade, and operating temperature has remained the same.  I say go with a Gen 3 SSD.  There is no reason to pay more for a drive that won't be able to operate at full speed...unless the intent is to someday use the Gen 4 drive in a future machine that supports Gen 4.

All that said, you may be able to get a Gen 4 drive to operate at full speed in a Vostro 5502.  A couple of years ago there was a guy on a forum with a Vostro 5402 (the 14" screen version of these machines), Core i7, integrated graphics only that claimed to get full Gen 4 speed out of a Samsung EVO 980 Pro SSD.  He posted benchmarks and output from a system info program (can't remember which one, but it was detailed) which showed Gen 4 support for his 5402.  His theory was that without the Nvidia graphics chip, PCIe bus bandwidth was increased for the NVMe slot which allowed Gen 4 support.  This is reasonable because technically these machines do have Gen 4 support (and Thunderbolt support as well).  Dell just neuters them and removes features so they can be positioned as lower end machines in their lineup.

So if your 5502 only has integrated graphics it may be worth it to try a Gen 4 SSD. If I can remember which forum this was posted at I will add the link to this thread.  I also vaguely recall that he was only able to get Gen 4 speeds out of one of the NVMe slots so if you go this route try the drive in both slots.