Warning: Long post
Over the past ~15 years I've developed pretty extensive experience with a few products and spent way too much time on the Autopia forums learning all I can about this. It's a rabbit-hole, don't go too far down it.
Long story short, Klasse and Duragloss are my favorites, with a slight edge to Klasse.
The two-part system of Klasse All-in-One (AIO) followed by Klasse High Gloss Sealant Glaze (KSG or HGSG for short) will last easily three months of normal driving. This from someone who subjects his cars to the daily abuses of a Minnesota winter. If you can layer the HGSG it will last easily six months, and up to a year with maintenance. By maintenance, I mean hand washing and then waxing as you dry using a dilute solution of HGSG. My recent formula has been 12oz of Meguiars Ulitmate Liquid Wax (also known as Synthetic Express Spray Wax) with 2oz of HGSG in it. I've just bought a bottle of Sonus Acrylic Glanz which is supposed to be Klasse compatible. I haven't tried it yet though. (probably tonight)
I also have extensive experience with both Duragloss and Zaino, which are very similar chemistries and product lines. Don't waste your money on Zaino, DG is at least as good and much less expensive. There are two reasons I prefer Klasse to DG. First, Klasse protects against acidic bug gut etching substantially better than DG (or Zaino), especially on paint protection film, which I have on my hoods and front bumpers. With DG you have maybe 36 hours to get the bugs off before a stain will be visible. With a reasonably fresh coat of Klasse I've waited a week without consequences. Mind you, here in Minnesota we don't have swarms of love bugs, which I hear are terrible for etching.
The second reason I prefer Klasse to DG is the way it protects and beautifies hard rubber and black plastic. You have to be careful with the AIO as it will stick to trim, though its relatively easy to remove. The HGSG though I deliberately put on black plastic and rubber. The mudguards and window trim of my 10 year old Subaru look brand new as a result. I've even gone to using my HGSG spiked quick-wax as an interior dressing, replacing my trusty 303. My Honda, by contrast has been on Zaino/DG, and some exterior trim fading is apparent. DG111 does work on trim, it's just not as well as KSG.
Now for the upsides to Duragloss. It's substantially easier to use than Klasse, especially #105 used with a dual-action polisher (DAP). Anybody who says synthetics are universally easy to use hasn't tried many. Klass is a real PIA if you don't know the technique. It must go on "whisper thin" if you're going to let it dry before buffing or you'll never get it buffed off. I use a wipe-on wipe-off technique where I don't let it dry. Duragloss also has the polish bonding agent (#601) which I consider essential to the system. Apply #105 with a DAP, then mix up an ounce of #111 with 0.2 oz of #601 in a small jar. If you arrange it right you can do three coats of #111 from that jar over the next ~3 hours which will give you an incredibly durable finish in little time. Applying a coat of #111 to the exterior of an average size car takes no more than half an hour.
If I want to layer with Klasse I have to wait at least eight hours for it to cure before applying the next coat, which means I have to plan my entire weekend around waxing the car. I have not yet tried polycharger which accelerates curing for Klasse the way #601 PBA does for Duragloss. I'm planning to try it in the spring.
The other thing I love about Duragloss is the completeness of their system of products, including rinseless wash, rinseless wash+wax, Aquawax for wax-as-you-dry and especially the bug remover, god do I love the bug remover. It makes bug removal really easy but does not remove the sealant the way most harsh products do. Lucky for me the bug remover seems equally gentle on Klasse as on Duragloss.
If you want more polishing action you can substitute Duragloss #501 (Marine & RV) for #105 as the priming step. Don't worry that it's a marine/RV product, car enthusiasts have been using it for years without consequence.
A couple years ago I conducted an experiment where I divided my Honda into four quadrants and used four different synthetic primer + LSPs on it:
Duragloss #105 followed by #111, both with #601 PBA
Finish Kare #215 followed by #1000P paste wax
Meguiars Ultimate Liquid wax primed with Meguiars Ultimate Polish
Klasse AIO + High Gloss Sealant Glaze (one coat each)
My notes from the winter time test distill to this:
Duragloss - Shines extremely well, very durable, good at shedding contaminants, easy to apply, mediocre on trim.
Finish Kare - Shines extremely well, very durable, excellent at shedding contaminants, difficult to apply (shows white streaks in seams of paint film), good on smooth trim, but tough to apply and sticks to textured trim.
Meg's Ultimate - Shines exceptionally when new, but fades, mediocre durability, mediocre contaminant shedding, easy to use but not particuarly good on trim.
Klasse - Initial shine is mediocre (looks like you wrapped the car in Saran wrap), very durable, good at shedding contaminants, difficult to apply, great on trim.
I've also used Opti-Coat 2.0 on my parent's cars and a couple of friends, also on my personal wheels. It's good for the casual owner who wants a car that looks good for a long time, but it only looks great for the couple of months after the coating. People say it sheds contaminants well, but my experience is its comparable to DG and Klasse, and not nearly as good as FK1000P. I'm considering trying Duragloss' coating on my parents cars now that Optimum no longer sells their durable coatings to the DIYer. Opti-Coat 2.0 lasted about 3.5 years on my parent's cars.
Sorry for the long post, I'm simplifying my system and getting rid of what I don't need, if you want any of the products mentioned above (except Opti-coat), PM me. Free to a good home, pay shipping.
