You say you have "a large collection" of Murano weights. I'd really like to see images of all of them - if that could be possible!
Within the Paperweight Collectors Circle I have met lots of members who have some Murano weights but I have not yet met anyone who has a large collection of them or who is able to readily identify the makers by examining the weights.
One of the problems is that most of the weights are "tourist / gift" items and they cover a wide range of styles and are produced in massive numbers. As far as I know, the Murano makers did not produce any "collector" or "limited edition" weights in the same way that, say, Caithness Glass or Perthshire Paperweights (to name just two well-known UK makers) have done.
To quote from Bob Hall's book, World Paperweights - Millefiori & Lampwork
, (published 2001)
With just a few exceptions the weights are mass produced by the thousands with little variation in design by each glasshouse.
That comment was made next to a photo of a Murano shop window display showing a range of large (about 4 inch diameter) millefiori weights which seemed to be of reasonable quality.
So, maybe you have more Murano weights than most of the collectors I am aware of :!: But I do know of an American collector and dealer who has a very large collection including many Murano. Some of those weights are illustrated in Bob Hall's book but no maker is given - just a "Murano" attribution.
As for specific details to consider when choosing "the best" examples:
1) I agree with Leni's sentiments regarding collecting "lesser" pieces, as I often do that particularly if a weight has a feature that I am interested in. (It's also how I collected my "Coloured Victorian" glassware - not because they were top quality and expensive, but because they interested me and added to my knowledge - as well as brightening up my rather dull sense of interior decor
2) Ideally, to be rated as "top quality" in terms of a maker's skill, where a clear dome is used, it should be perfectly clear with no evidence of "wreathing" or "striations" or any "crystalised lumps" within the glass. The dome should magnify the interior design such that it shows clearly and evenly. No unsightly distortions should be visible in the magnification, even from angled profile views.
3) The interior design elements should not have any breaks or misalignments that detract from the overall look of the weight, or that draw the eye immediately to them. It is not absolutely necesasary to have "perfection" in the setting of the canes or lampwork, although many makers of "collectable" weights will always try to acheive this.
4) The base should be finished in a way that allows the weight to rest in a stable position, whether it is set on a flat horizontal surface or dsplayed in an angled stand.
5) The surface of the weight should be as clean as possible, bearing in mind its age and the effects of normal handling. If a weight has been ground or polished to remove scratches, chips or bruises, then the dome should still have a well-formed profile. Any "flat spots" or uneven grinding will alter the magnifying qualities and may spoil the overall look of the weight.
6) Having covered some aspects of "technical quality", there is also "rarity" to consider. With antique French weights, it is now quite difficult to find very good examples at "cheap" prices (although it does happen on a few rare occasions), so the technical quality often takes a back seat when it comes to "getting one for the collection". The same is true of certain types of weight from more modern makers.
So, this brings us straight back to your question in context of the Toso "flower" weights you have shown.
In my view, the "daisy" weight to the left is better than the one on the right - because the colours are more contrasted and the flower petals are generally better set. But the one on the right has the benefit of showing the green ground better than the other one and is therefore more aesthetically pleasing to me. But if either of them have faults of any kind in the dome or the base, this would make me seriously consider whether it was worth having.
For the "roses" weights, the one on the right wins for me. Its elements are smaller and much better controlled and I find this visually pleasing, even though though the colour of the roses is rather "watery". The other one just looks "sloppy" to me, but if it was the only one I had seen in years of searching for an example, I would not hesitate in buying it.