I'd be very interested in hearing what you feel are the 'significant' advantages of C1 over LR, and what the current deficiencies are.
Off the top of my head (I don't keep a list - things change too frequently):
- Better Color (subjective but found consistently enough by myself and a high enough % of customers to say with confidence) especially with strongly saturated colors, purple/pink/red crossovers, skintones, and in steep tonal transitions like strongly side-lit portraits.
- Better tonality especially in deep shadow detail
- Noise/Grain/Texture/Microcontrast which looks better if your aesthetic is to allow grain but want that grain to be gaussian, fine, and film like rather than clumpy and digitally blob-like. On the other hand if you're shooting fairly high ISO with a dSLR and want the "clean commercial look" LR4/5 does a better job of what I'd call the "sledgehammer" approach of noise reduction if you abhor noise/grain and want no part of it.
- More pro tools for tethering:
--- live view
--- camera controls
--- fixed-focus windows (e.g. for four-corner-and-center analysis in a product/catalog environment)
--- focus mask (especially powerful for first-round edits and shoots involving tilts/swings)
--- overlay (great when matching another shot, or fitting a layout, also useful for random applications like matching color in art repro settings or corporate color settings)
--- more detailed/flexible controls (assumes/requires more education and a desire for more power/nuance over first-glance-simplicity) like full RGB levels with numerical entry, more specific noise reduction sliders,
- LCC tool which is required for tech cameras, but useful in a variety of niche applications including art reproduction and catalog shooting and automatic dust removal
- Chromatic aberration and purple fringing tools that work better on a broader range of files with far less work/twiddling
- A better laid out system for local adjustments (I think I'm in the minority here)
- Far more customization of the user interface, especially handy on very small (e.g. 10" MBA) or very large monitors (e.g. 30" Eizo) or in multi-monitor environments. Every tool can be floated/added/removed/collapsed or put on a second monitor. Including keyboard shortcuts which are every power user's dream.
- Better laid out tools for manual keystone/perspective correction (also auto-integration with newer Phase One digital backs, though that only helps those shooters)
- Completely/immediately portable session layout. For anybody who uses multiple computers in their workflow this is a huge help. You don't have to export/splice/import/merge or do anything at all to move a C1 session from one computer to the other. Everything resides in the folder.
- Massively better color editing tool (Color Editor) which is harder to learn but far, far more powerful than the LR equivalent.
- Far more flexible process recipes/definitions/presets. I've set up some very sophisticated ones for clients which saved them many many hours every month.
- Much better support. P1 has no "low level" support folks. You don't need to get "elevated" to get past the person who can only really help with basic problems. Support cases are answered in hours (very often faster), not days. Dealer support (at least the value added dealers who have dedicated tech departments) includes weekend/holiday/night/crazy-emergency support and includes workflow/productivity style help not just "this button doesn't work"
- Faster processing in most cases (somewhat computer configuration dependent) with accurate time-to-completion times and preemptive scheduling (you can push a job to the front if you have a long queue that isn't a priority)
- sometimes (though not always) being a few weeks behind LR on support of brand new cameras (since they are implementing the full SDK of the camera allowing live view, camera controls etc).
- higher learning curve (often requiring capture one classes
- no prosumer features like Book/Map
- pretty limited print functionality (some printing workflows C1 can handle on it's own, but more could be handled in LR on it's own)
- spot removal tool is as good as LR4 but not as good as LR5. Not a deal breaker for my own personal work as I'd be hard pressed to not finish an image in Photoshop which requires pixel-level retouching, but for some workflows probably notable. Maybe C1v8?
- no history panel (maybe C1v8?)
- no highlight/shadow recovery in local adjustment system (you can accomplish the same thing with exposure/contrast tools but it requires more work)
- small ecosystem of education/training like with Adobe. This is greatly alleviated by having a good dealer who can easily answer your confused question when google/youtube fails you.
There are many more reasons (on both ends, pros and cons). But in general I see C1 targeting the pro market and making image-quality and pro-tools a high priority of design while LR tries to target pro and prosumer at the same time with the expected results of doing both quite well, but neither excellently.
I'd NEVER tell someone they should just run out and buy Capture One (or any other software for that matter). There is a 60 day fully functional trial for a reason. If it's not clear that it will benefit you enough to justify the cost then you don't spend a dime.