A NAS and personal cloud are different. A NAS is simply network attached storage, it's a hard drive connected to the network (Intranet), for the average consumer it'll be relatively slow however a good backup/archive solution. A personal cloud on the other hand is connected outwards to the internet, and is accessible outside the network. I never use a personal cloud because I have dropbox etc. which provide a much faster and more stable/secure connection.
Unless it's a high end server grade computer with SSDs and a 10gig ethernet connection, it'll be relatively slow. A fixed HDD is always a much faster way of transferring data. But, I love NASs for the simplicity and always connected behaviour, they make fantastic backup options as it negates the need to find it and plug it in (Which causes you to not backup).
OP: Things depend on how 'fast' you want it vs. how 'fast' you need it vs. how much you're happy to pay. A TB3 SSD will be lightning fast, cost a fortune, and arguably provide little actual benefit as I'm assuming you're transferring hundreds of smaller individual raw files? A USB3 SSD will probably be your best all round option. I'm personally still using an older WD USB3 HDD and find the transfer speed absolutely fine, I can wait a few extra minutes and grab a coffee when backing up images, and this thing was closer to £40 than the £400 it'd cost to gain those extra minutes (Plus I like coffee).
Basically, work out your budget and what you're happy to spend, and then seek the fastest within that, but again stick with branded to get somewhere near advertised speeds.
