In ground, apparently you can dig a hole to uncover the roots to cause the plant to dry out and cause stress to make it flower, but its much easier in pots were you just dont water them Its that cold over here that ive not had a problem with the citrus flowering so ive not tried, but i do have a couple of bears lime trees that have flowered and fruited like a lemon tree , continuously flowered since last june under the growlights, i though they must have been lemontrees miss-labled but they are limes On other fruit trees such as pear,plum and apples it seems normal that if a few years after planting they havent flowered they chop the roots with a spade to stress the plant into flowering!, that sounds a bit drastic to me chopping the roots to cause a plant to flower

Evan is right; those clusters will soon enough drop some if not all; the fruitlets will turn yellow and fall off. Most citrus are good at self thinning; the young Meyer not so good, until it gets to be about 5 years old.

According to the "book" and what I've read thornless don't yield as much. Whether it's enough to matter to the average homeowner I don't know. Also IME Persian Limes (especially) & Key Limes are very underrated for their cold hardiness. TRUE Lemons are over rated. I have about 20 citrus trees in the ground and my Tahitian lime is one of the hardiest & most cold hardy here in zone 9B. The only citrus trees I have ever lost to low temps were a full sized Harvey Lemon and a mid sized Varney Navel tree back in our record 2010 freeze here when he got down to about 20. Nothing else even got burned. I have seen a lot of nurseries saying Tahitian limes are cold sensitive and I have not found that to be the case. Lemons I have.

Sorry to have no advice in regard to which is best, but have you tried posing your question on the Citrus forum yet? I have a Mexican (a.k.a. Key) lime tree I grew from seed, and it's given me loads of fruit - way more than I can use - even tho it seems to have some of the maladies common here in FL. It's very thorny, and fruits several times a year. If you really don't want thorns, fewer fruits may not be a bad thing.