Is there any significant differences, risks, benefits, of using the Arduino as an ISP versus using an FTDI board?
I've been uploading sketches to a bare ATTiny85 chip using Arduino as ISP, but I also have an FTDI board sitting nearby. Haven't yet bothered with the FTDI board, since after I set up the Uno (upload ArduinoISP sketch, capaciter b/w Reset and GND) it has done everything simply. Is the FTDI route better somehow or simpler somehow?
As ron_sutherland said, ISPs allow you to change the fuses(only happens on Tools > Burn Bootloader). This can be useful but it also frequently pops up in the forum that someone "bricks" their chip by setting it to use an external oscillator when none is present, in this case you need to connect an oscillator or external clock source in order to set the fuses back to the internal oscillator.
The benefit of using a programmer is you can burn bootloader, set fuses, and you can upload without a bootloader, freeing up flash which is very important with the ATtiny85.
There are some quirks depending on your programmer(or even programmer firmware version). For example, with Arduino as ISP if you try to do Sketch > Upload Using Programmer to an Arduino Mega the program never runs unless you change the BOOTRST fuse. You would not encounter that issue using the FTDI.
The other benefit of using the FTDI is that typically people are using Serial for debug output, etc. anyway so you get upload and USB-serial interface in one device. With an ATtiny85 you're less likely to be using serial anyway so again not really much benefit.
I'd stick with your Arduino as ISP(or better yet buy/make a dedicated programming device) for your ATtiny85 but if you start working with a larger bare chip definitely consider the benefits of the FTDI.
I would prefer to use FTDI for development and then once things are finalized use a programmer to upload the finished code. This means less code running on the device to mess something up and no bootloader delay on power up/reset. On the other hand, if you're selling devices leaving a bootloader on it could make it more accessible to people who might have hobbyist level interest in hacking or updating the firmware.