בין אדם למקום vs בין אדם לחבירו

In an instance where someone can do one of two mitzvos, one interpersonal and the other between man and G-d - which one should he prefer. Example: Hashavas aveida [returning a lost object] vs. taking the lulav. The Pri Megadim discusses a conflict between birkas kohanim and returning a lost object. He says that since birkas kohanim is three mitzvos it is preferable. However, according to the Rambam it is only one mitzva and being that hashavas aveida is both an מצות עשה and לא תעשה and birks kohanim is only two mitzvos עשה  - hashavas aveida wins.

According to that reasoning, hashavas aveida also trumps lulav because lulav is also only an עשה while hashavas aveida is also a לא תעשה.

The gemara in Bava Metzia [30a] says that the עשה of השבת אבידה doesn't override the איסור of tumas kohanim for 2 reasons. 1] An עשה does not override a לא תעשה and עשה. Reason Two] An איסור doesn't override ממון, meaning the בין אדם לחבירו of ממון doesn't override לאווין. The Ramban there explains that the reason is that a person should be מוחל on his money in order to prevent the necessity of overriding the איסור. According to that, when השבת אבידה conflicts with מצות לולב the person should be מוחל on his money in order to allow for the fulfillment of the mitzva of lulav [as he would for a לאו - see the Ramban].

Apparently, our question depends on the two answers of the Shittah Mekubetzes [Ba"M 32b] on the gemara that asked how can one possibly think that one should listen if his father told him not to return a lost object, השבת אבידה is both a לא תעשה and עשה?

Asked the Shittah - Kibud Av is in the realm of איסור while השבת אבידה is in the realm of ממון and we learned earlier with respect to a kohen returning a lost object from a cemetery that ממון is not דוחה איסור. So here too, the ממון of השבת אבידה should not have any importance when it conflicts with כיבוד אב ואם?

Answers the Shittah 1] אבידה is more חמור because it has a לא תעשה and עשה. Number 2] Kibbud Av is more lenient because the pleasure of the father is considered ממון.

According to the first answer he should NOT the lulav when it conflicts with השבת אבידה because אבידה has a לא תעשה ועשה and lulav is only an עשה. According to the second answer he should take the lulav because השבת אבידה is ממון which is more קל than the mitzva of lulav [just as it is more קל than איסור - see the Ramban on דף ל].

[One may also add that there is a רא"ש quoted by Reb Elchonon in the Kovetz Maamarim who says that bein adam lachaveiro is more important than bein adam la-makom because every bein adam la-chaveiro is ALSO bein adam lamakom.]

  There is a lot more where this came from  - see the sefer בני ראם סימן נג by HaGaon HaGadol Rav Avraham ben Gita Genachovski who needs a refuah shleima - please daven!!