I agree with Bamboo. Aesthetics is "...in the eye of the beholder...". What a lot of people think is 'what looks good...' is as individual as each person. Not true...there are RULES artists, designers...Landscape Architects...follow to produce something that 'looks good'...to most of humans, to the average human. RULES are made to be broken...of course but only someone who has mastered those rules can be successful breaking the rules...or very lucky. For example; the simplest rule in composition (of a work of art painted in oil, graphite, sculptured in stone...or sculptured in soil and plants...) is to keep MOST of the elements of composition (...rhythm, form, texture, color, line quality....) THE SAME. Consciously choosing one or two elements to BE DIFFERENT in some way to 'drive the eye of the viewer' across the composition in a meaningful way eliciting memories and feelings...or whatever an artist can do to be...a memorable experience when seen, felt, smelt by another human.
Edging between plant beds and lawns such as concrete, plastic, big river rock, white sand stands out strongly. Best used by professionals otherwise these elements in a landscape aren't really functional and become distracting. Rock, concrete, plastic also provide 'housing' for lots of pests such as slugs, snails, millipedes, pill bugs, etc. Soil-colored trenches provide a crisp, natural and functional transition into beds. Your EYE sees the edges of a lawn, first. As long as the center is homogenous and fine-textured, and you follow the rules for delineating your lawn's edges...you can use finely crushed gravel instead of grass and the product will be beautiful.
Your time spent re-establishing your edges with a flat spade or half-moon edger once a year or every couple of years will be far less than any other solution that I know about. Otherwise, I use PT 2x4's (scored to bend if you have curves) between any gravel paths or graveled flooring in your landscape.
The 'rule' for designing edges of lawns is to use either straight runs with 90 degree angles or sweeping curves with radius sizes reflecting the size of your lawn; small radius for a small lawn and large radius sizes for large lawns. This also is reflected in the size of plant beds in relation to the size of the property and lawn. When a curve is made (use upside down paint and string attached to a stake at the center of the circle of which the radius is a part) make sure only ONE radius is used...as long as one keeps in-scale, you can change the length of radius for each curve separated by the center of the radius changing from 'inside' to 'outside' the circumference of your lawn No 'compound' curves. Looks like a mistake...to a professional, anyway.
Whenever one sees a curve in nature, there is a reason it changes direction such as a creek curves in a the opposite direction to get around a less-erosion-prone rock substrate or a huge boulder delivered in-place by a glacier or ancient volcano. Even if we know nothing about geology or science, our subconscious gets 'nervous' when we see lines that don't make sense. Same is true when our gardens have so much going on within the composition (for instance, too many textures, different colors, changing shapes within one composition). The human brain, as I was taught a long time ago so the details may have changed but still will help in understanding my point, can only 'multi-task' 3 chunks of dissimilar information at a time...comfortably...for the average person. If there is too much information, our stress level increases (unless of course you are ADD where increased stimulation actually helps us focus) and we feel less comfortable than before experiencing a poorly composed and overly complicated garden. Something I recognize when visiting nurseries. The smarter nurseries 'group' plants which helps clients to reduce the stimulus of disparate objects...provide 'eddies' where plant material is planted in homogenous swaths and chairs, tables...familiar stuff so those that are less experienced with plants can reduce their input of stimulus and revive before going back out into the nursery. Another example of how one's environment affects us (subliminally) are stepping stones or concrete pavers or any other part of the 'hardscape' are situated in a way that our subconscious 'remembers' has been or could be...dangerous.
Imagine concrete pavers formed like a diamond. Take a square shape and push two opposing corners towards one another. That's a diamond shape. If the long axis is laid parallel to the direction of the path we see a sharp point coming at us as we travel the path. Most people will notice the novel shape and think it is clever. A professional will appreciate this only if this was an attempt to make the person walking the path to look down and focus on the path for enough time to change the path's material for a finer textured, wider, safer path which causes this person to look back up and be surprised and awed by a breath-taking vista (immediate, intermediate as well as long distance 'views'). This manipulation is one of the hallmarks of 'Japanese Gardens'. Curvey lines without apparent reasons for the curves will trigger 'snake' connotations in our minds. Riding my horse and coming upon a group of willy-nilly curves at the edge of this lawn...actually spooked my horse into a 180 degree hind-end turn (ouch, I actually went back and fixed their lawn...).
Back to your yard...'edging' that one can readily notice because it's unusual color, texture, meaningless curves...will add unnatural elements to your yard. If you are not a trained artist, designer or Landscape Architect who all are trained in 'artistic composition', I doubt installing anything other than hand-trenched edges, maintained with a line-trimmer and re-established once every other year will look...awful. Feel even worse.
Lastly, edges along the drive and concrete walks, concrete planters or even along the 2X4's enclosing gravel...the grass should go right up to the edge. No intermediate edge in-between. What a lot of work the weeds must or will cause! Think like a weed seed parachuting around looking for a home to grow. What could be better than a flat surface that gets fertilized, regularly watered, full sun and no other competition!? The main job of a lawn is to provide a green, living surface for us to use. Vigorous lawns out-compete other plants, provide shade to eliminate germination of seeds and deep watering/drying out of the soil in-between watering intervals trains grass to root deeper, get at water and nutrients while baby weed seeds trying to germinate without moisture are thwarted.
Hope this was helpful, landscape as medium is so inter-connected with all the different branches of science, the answer to one question is never going to be 'simple'...grin. Maybe it's just hard for ME to make shorter answers...