SSD vs SD card expansion for MBA 2014?

An SD card is extremely slow compared to an SSD. It isn't something you want to run a program from or to store data that needs to be updated frequently. (Saves are slow.) But for data that is only read - like music and movies - it is a good fit. I've been using an SD card on my MBA to store media for years.

I use a BaseQi SD card adapter in my MBA paired with a 200 GB micro SD card. I use it to store MP3s for iTunes and to have a place for Time Machine to back up to.

I agree with dwb - when compared to the SSD, there is no comparison. It does fine for streaming music, but when it comes to more vigorous use, especially non-sequential reads, it really does lag. Remember that in the MBA, the card reader is running through USB, whereas the SSD is running through PCIe...a much faster protocol.

Another point - when I started keeping that BaseQi installed, I found my battery life took a small but noticeable hit.

So like most everything in life, there are upsides and downsides. Using the SD card is certainly less expensive than a new SSD, but performance isn't as robust as an SSD either.

What is 'pretty good performance)

What actually is its speed.

Post a link to something that notes the actual speed of transfer. LOL

I looked up the Transcend that you noted, it is very much slower than a real SSD.

Transcend: Max Read: 95MB/s, Max Write: 60MB/s

OWC SSD: Max Read 550 MB/s, Max Write; 550 MB/s

Yes indeed, you pay less and in return you get less.

According to the spec it's even slower than the Transcend, but if you want to rely on YouTube go right ahead.