Answer: I think just about all lilac varieties of Syringa vulgaris are going to be potentially subject to problems such as mildew, for example. The severity will depend on the lilac's location (an open sunny position with good air circulation and also away from a frost pocket that also becomes relatively humid in summer is best), the soil moisture levels (it seems worse in a dry year) and also humidity levels (drier air is better) and to some extent cultural conditions ( overfertilizing can lead to over luxurious growth which can be more susceptible to all kinds of problems, evening watering or wetting the foliage can make it worse) and general sanitation (thorough clean up of diseased foliage each fall, replacing or topping up the mulch with a fresh layer each spring to try to limit reinfection, proximity to other infected plants, etc.) and pruning (annual thinning at the base to keep the plant open to sun and air movement).
By the same token, suckering is to some extent a function of the variety and its balance or match with the given rootstock, it will also vary depending on whether the plant is cutting grown or grafted. Again, proper annual pruning can go a long way towards minimizing the effects of this and toward maintaining a healthy plant.
With regard to fragrance, in my experience that is truly in the nose of the beholder, so to speak. To some people all lilacs are almost unbearably fragrant, to other people there are discernible differences from variety to variety. As with roses, I think this is a matter of personal taste and preference and can only be appreciated by first hand experience. I suspect too that the scent (and color too) changes with the weather, the soil, the time of day, and so on. For this reason I think it is important to see and smell the plants individually in person before making a selection -- there are hundreds and hundreds if not thousands of varieties!
In terms of hardiness, lilacs at the basic level are very cold hardy and in fact are sometimes used as windbreaks. According to Michael Dirr's well respected "Manual of Hardy Landscape Plants" lilacs (S. vulgaris) is hardy into zone 3.
Of the plants you mentioned, Charles Joly tends to appear on many lists of "best lilacs" and is considered to be highly fragrant, it is also a lovely double flowered form with a rich magenta coloring and a long standing "tired and true" variety so it might be a good choice for you. Apart from that, you might want to experiment and see what works best for you in your own yard and growing conditions. Also, your local county extension and professional nursery personnel may have some suggestions as to varieties that do particularly well in your local area and then you could examine those in person to make your selection.
You have asked some excellent questions and unfortunately, the answer is sort of an "it depends" and "in my opinion" kind of a situation instead of a clear cut or straightforward "do this." I hope this helps you in your decision making process.
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