Great question! I love Van Engelen and have found them to be a reliable source of bulbs. I haven't ordered from Scheepers since I like to buy bulbs in bulk. Otherwise, I also like the following:
1. Brent and Becky's. A great selection of bulbs, including fall and summer blooming bulbs. Prices on the higher end but quality is superb.
2. Odyssey Bulbs. My absolute favorite "boutique" vendor. This place has bulbs for the collector and connoisseur, many of which are available no where else. Prices seem high but are actually quite reasonable given the rarity of the bulbs, the volume discounts and the free shipping. Quality is out of this world.
So, the above 3 are my favorites. A lot of people *LOVE* Old House Gardens but, at the risk of being lynched, they are not one of my favorites. True, they have a great selection of older commercial varieties, but their prices are astronomically high. Many things they offer can be purchased for much less money elsewhere and be of exactly the same quality. Even the ridiculously priced White Flower Farm sells some OHG varieties for half the price.
A case in point. Last fall, I ordered Lilium regale, Lilium speciosum rubrum and Lilium speciosum album bulbs from Old House Gardens. I really splurged on these because I thought I was paying for exceptional quality. Later, I decided I wanted a few more of each so purchased the same bulbs from Van Engelen for less than half the price of OHG. It was not even Van Engelen's end of season discounted price, either!
Well, surprise, surprise! The bulbs received from Van Engelen were exactly the same size and quality as those from OHG. In fact, the Van Engelen bulbs arrived in slightly better shape since they were in individual bags of 5 bulbs with peat moss to serve as padding, while the OHG bulbs arrived thrown together in a single plastic bag with no padding. Some of the outer scales of the OHG bulbs were bruised because of this.
There has been absolutely no difference in performance, height, healthiness, perfume, etc., between the bulbs from the two companies. I am nearly positive they get these bulbs from the same supplier. The only difference is that OHG repackaged them, attached a cute tag with planting instructions and then overcharged for them. Hmmmph.