If you have Android Phone with any brand, the phone might have come with 2GB Memory card. The Mobile phones will have the option to upgrade the Memory card depending on the needs and also Phone support level.
I own a Motorola Defy plus android phone which came with 2GB Memory card. It can be upgraded up to 32GB, so recently i purchase a 8GB Memory card from amazon and inserted the card to the phone. Though the Phone recognised the Micro-SD card and also showed the capacity of the Micro-SD Card.
But the problem was that the phone started responding very slow and was taking too much to read the applications. Mobile Games was not opening intime and all of sudden the performance of the phone became very slow.
Removing of the Micro-SD card, the Phone performance was good. I had a doubt that the Memory card could be faulty, this could the read and write operation on the Micro-SD.
Inserting the 2GB Memory card into the phone the performance was good.
Solution to fix the slow android phones with larger memory capacity:
The Memory card should be formatted with the android OS, this helps in creating the File system on the memory card which will create file structure.
To Format the Memory card :
Place the card in the phone, open settings > storage > unmount sd card > format sd card.
The Memory card automatically gets mounted.
Now the Phone performance is very good and able to read the data on the Memory card with much faster.