I am the author of SdFat.
The Arduino SD.h library is a wrapper for a very old version of SdFat so it is missing a number of bug fixes.
SdFat has better native SPI support so is often faster.
A "SanDisk MicroSDHC 8GB Extreme Pro" is not likely to be faster than cheaper cards. High performance consumer cards are optimized for very large, many MB, transfers using the 4-bit SDIO bus. Many less expensive cards perform better than these high end cards on Arduino with smaller transfers using the 1-bit SPI bus.
Industrial cards optimized for embedded applications give the best performance.
Only testing with you application will determine which card preforms best.
Here are the SdFat bench test results for several cards on Due using 512 byte reads and writes.
Full size 8GB Extreme Pro
Buffer size 512 bytes
Starting write test. Please wait up to a minute
Write 242.81 KB/sec
Maximum latency: 81073 usec, Minimum Latency: 1496 usec, Avg Latency: 2106 usec
Starting read test. Please wait up to a minute
Read 752.96 KB/sec
Maximum latency: 3244 usec, Minimum Latency: 594 usec, Avg Latency: 677 usec
Amazon basics 8 GB microsSD
Buffer size 512 bytes
Starting write test. Please wait up to a minute
Write 252.65 KB/sec
Maximum latency: 285502 usec, Minimum Latency: 1029 usec, Avg Latency: 2023 usec
Starting read test. Please wait up to a minute
Read 1299.29 KB/sec
Maximum latency: 2562 usec, Minimum Latency: 323 usec, Avg Latency: 391 usec
A 1 GB ATP Industrial grade card AF1GSDI-ZAEXM ATP Electronics, Inc. | Memory - Modules, Cards | DigiKey.
Buffer size 512 bytes
Starting write test. Please wait up to a minute
Write 1104.17 KB/sec
Maximum latency: 63529 usec, Minimum Latency: 395 usec, Avg Latency: 461 usec
Starting read test. Please wait up to a minute
Read 2206.39 KB/sec
Maximum latency: 452 usec, Minimum Latency: 228 usec, Avg Latency: 229 usec
Wintec 2GB Industrial SD http://www.wintecind.com/OEM/Flash/SD/H6.html.
Buffer size 512 bytes
Starting write test. Please wait up to a minute
Write 1289.91 KB/sec
Maximum latency: 2439 usec, Minimum Latency: 348 usec, Avg Latency: 395 usec
Starting read test. Please wait up to a minute
Read 2865.15 KB/sec
Maximum latency: 359 usec, Minimum Latency: 175 usec, Avg Latency: 176 usec