It is all personal preference. Some stay exclusively with Golden, or Silver, or Bronze etc...
As to the "value" of Moderns, variant covers are the lucrative aspect of this period of collecting. The artist, character and rarity are all factors. I believe some will hold their value, others not so much. You don't, however, have to wait years and years to flip some of them.
The Watcher count on many high-priced items on Ebay alone indicates strong interest.
I personally have an interest in Silver/Bronze and Modern. I have 9.8's of various stable issues (eg. ASM #129, GSXM #1, IH #181) but have also invested in some Modern variant gems, such as Moon Knight #1, Thanos #13 etc.
Each to their own.