Price: Kensington Caviar is more expensive at £12 for a full sized bottle but you can buy the set containg the Kensington Caviar Base & Top Coat 8ml each for around £12. Seche Vite is just under £10 (depending on where you purchase it from) for 14ml.
Finish: They are both fast drying top coats. On my nails they are both touch dry in the same amount of time. Kensington Caviar has a slight pink tinge to it but has never altered the colour of any polish I'm wearing. If anything it makes the colour more intense. Seche Vite is clear and also makes the colour more intense. They both leave the nails seriously glossy but Seche Vite has the edge as the formula is thicker.
Formula: Seche Vite is very thick and gloopy, even when you've just opened a brand new bottle. After the first few uses I noticed the formula started to dry out and get even thicker. I've read reviews saying that even when the bottle is half full it's almost unusable and you will need to use a product like Seche Restore. From what I've read, Seche Vite can be used on wet polish. I've tried this and ended up with streaks, smears and the brush was covered in whatever colour I'd used. If you don't apply enough, it drags across the nail leaving an uneven finish but if you use too much it pools in certain areas and leaves the sides of the nails looking crusty. It also caused major shrinkage at the tips on certain shades. Kensington Caviar is only slightly thicker than a regular top coat, spreads across the nail with ease and doesn't get gloopy untill the bottle is almost finished (even when it is gloopy it can still be used)
Longevity: Seche Vite cracked on my nails, peeled off like a sticker and didn't make my mani last any longer than if I didn't use a topcoat. Kensington Caviar does prolong the life of my mani but certainly isn't a game changer when it comes to wear time. This doesn't bother me in the slightest though as more often than not I'll change my nail colour before any chips or tip wear appear.
For me, Seche Vite isn't worth the hype. I can see why a lot of people love it as it leaves a really gorgeous, glossy almost gel like finish on the nails but the problems with application make it more hassle than its worth plus the smell is horrendous. It even comes with health warnings!
Nails Inc Kensington Caviar Top Coat still remains in my Holy Grail section and I can't see that changing any time soon but another great fast drying top coat is Sally Hansen Insta-Dri. It works in the same way and is a more purse friendly option.
Whats your Holy Grail top coat?
Have you tried either of these?