Hi.

I've a 64bit processor (AMD).
I love Linux Mint. My questions is:
can I safely install both 32 or 64 bit version?
Should I notice better performance with 64bit? Thankyou

Yes, you can safely install either. The main advantage to 64 bit for
personal use is that it can make better use of more than 4 GB of memory.
So if you have 4 or more gigs, it's better to install 64 bit. If you
have less than 4 gigs you could install either, and you won't notice
the difference.

Actually, I have found some small performance advantage to running 64 bit on fast AMD multi-core processors regardless of the memory. Also, a certain slight penalty on certain slower INTEL processors with 4G or less memory. Neither effect would make the decision for me by itself, and my testing applies to my specific mix of functions and applications and may not pertain to yours. The differences are generally not enough for anyone to notice unless they are running benchmarking tools.

Certain vendors that I deal with are starting to release early for the 64-bit kernel, and later (if at all) for 32-bit. As a result I get faster access to new features if I load the 64-bit. For my purposes, this is much more significant than the performance issues.

File-system efficiency (storage speed) seems to make a much greater performance difference. I like my data partitions to run EXT4 for the best compromise between performance and security. XFS performs as well or better for some things, but I have had problems recovering data when encountering file-system corruption. To my surprise, I found I achieved better performance using RAID5 than with RAID1, though only marginally better than using native disk.

SAN performance using RAID5 or RAID6 on an efficient, well designed (expensive) SAN blew away all native disk performance measures. Running intense services on a machine seemed to display a near doubling in performance when storage was moved to SAN. I wish I had a business case to support my using a SAN at home, but the $$$ gets in the way. ;-)

Conclusion: look at the bigger picture. Examine speed of storage, type of storage, type of CPU, applications, vendor factors (hardware, application, and OS). If the decision is still not clear, go with 64-bit to better support possible future expansion.