XC3 are the " cheapest " ones and I don't mean in a wrong way, but basically less features (like some monitoring sensors) that you don't necessarily need as a normal user, and overclock from factory is a bit lower too (which doesn't mean you can't do it yourself, also GPU Boost already boost the card by itself trying to give the best clocks possibles regarding how hot is the card and how many power it consumes already). The card is also 2.2 slots and around 28cm long for the XC3 while being 2.7 slots and around 31cm long for the FTW3. 

Look also changes from the XC3 to the FTW3. And prices, obviously. 

In addition to the above point, the power delivery on the FTW3 is beefed up in comparison to the XC3, with 3x 8 PIN Power connectors vs 2x on the XC3.  The cooling solution is also larger and in theory better.  The FTW3 also has more LEDs.
 
The FTW3 is EVGA's mainstream overclocking card, while the XC3 is their mainstream lower end offering.  Both are great cards.  I am currently running a 2080 XC3 Ultra and it is a great performing card while still being quite.  The XC3 line is the least expensive of the EVGA cards, but I do not consider it a budget card, all EVGA cards are well made and perform well.

homerjs225
If I'm going to add a waterblock and OC in the future does it make sense to get the XC3 since the boost clock is the difference vs the FTW?

If you're planning to do all that then get a FTW3 3080, 3080 Ti or 3090. The XC3 can't overclock as well because it doesn't have access to more power. 
 

CausticEd

homerjs225
If I'm going to add a waterblock and OC in the future does it make sense to get the XC3 since the boost clock is the difference vs the FTW?

water = ftw3

You and @KingEngineRevUp like FTW3.  Was thinking of an EK waterblock or does it make sense to stick with EVGAs block?

homerjs225

CausticEd

homerjs225
If I'm going to add a waterblock and OC in the future does it make sense to get the XC3 since the boost clock is the difference vs the FTW?

water = ftw3

You and @KingEngineRevUp like FTW3.  Was thinking of an EK waterblock or does it make sense to stick with EVGAs block?

If you can get the HC FTW3, then do that, you'll save money. You're not paying for a heatsink on the card that will be removed and stored away.