You can pretty much expect the speeds that your provider has mentioned while you are getting the seedbox, just in case you are not getting those speeds please continue reading.
FTP Speeds:
If you are getting slow ftp speeds chances are you are accessing the ftp when its most congested, many providers are facing heavy congestion.
Cheap Seedboxes advice: Try to use the FTP in times other than North America, 8pm – 2am when there is maximum congestion in traffic, you can set up your ftp work at night when you are sleeping and you can surely get better speeds.
Upload speeds: If you are getting slower upload speeds they might be one f the folllowing reasons
1. You might have reached your bandwidth cap on your seedbox provider.
2. The torrents you are seeding done have many leecher.
3. Temporary network congestion
In case you have a doubt you can also send in tickets, the seedbox I have recommended have real fast replies.
3. Download Speed
1. Generally downloads are not capped by seedbox providers, so most probably soem other issue is affecting it.
2. The torrent might not have many seeders.
3. Temporarily bandwidth capped for the seedbox provider.
So just before you jump into a conclusion see to it that, these issues are not affecting your speeds and even if you find out the issue discuss with your seedbox support team and then take a decision on where or not to shift.